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THE GEOLOGICAL MAGAZINE. DECADE VI. VOL. III.
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FACING PAGE
. Restored Skeleton of Stenomylus hitchcocki, Loomis
Saurostomus esocinus, Agassiz; Upper Lias, Holzmaden
. Terebratulid Shell-structures
Map of the Fluvio-glacial Gravels, Thames Valley . Portrait of Arthur Vaughan, B.A., D.Sc.
Chalk Polyzoa
Two Obsidianites, Singapore
Lower Lias Ammonite, Dorset .
Tridymite and Quartz, Iceland
Chalk Polyzoa
Portrait of Dr. John E. Marr, F.R.S.
Some Wealden Sands
Pit and Mound Structures developed during Sedimentation Chalk Polyzoa
New Extinct Bird, South Carolina .
Voleanie Rocks, Iceland .
Triassic Fossils, Leicestershire
Chalk Polyzoa
New Guinea Corals .
1 ol
fay h te
LIST OF ILLUSTRATIONS IN THE TEXT.
PAGE Trail and Underplight . : : ; : : : ‘ : : 3 Wax and pitch =. d : : ; : : : ; : : 5 Sketch-map of Permian formation in Maritime Alps . : : > 10 Sections of Permian formation, Maritime Alps . : : ; Beane ab Map of West Cumberland . ; F : Q : : i 5 IS
Diagrams showing amount of water and sulphuric acid in St. Bees Sandstone : ; ‘ : : : F ; : : A vcs HS)
' Diagrams showing variation in number of puncte of Terebratula punctata and T. biplicata : ; 5 3 : : - 55 Sections of overflow channels, Murk Mire Moor . 6 : : aE: Plan of adoral surface of Lovenia forbesi . : : 3 : . 102 Second figure for comparison : : 3 i F : : . 103 Ball and pillow-form structures in rocks : ; : 3 : . 147 Shell-jointing in sandstone . : : ‘ 5 ; : : . 148 Ball structures in sandstone . : : 5 : : : : . 149 Sandstone ‘ball’, Tyddyn-main . A ; 3 : ‘ : . 149 Contorted layers in sandstone 3 ‘ F : : : 4 . 150 ' Diagram showing curved cleavage : 5 : 3 : : . 153 Folded layers of sandstone and shale . : : : é F . 153 Sandstone in shale ‘ ; : ; ; ; ‘ : : . 154 Map of crystalline rock-areas, Piédmont : : : : : . 199 Drawing of aggregate of Pl. IX, Fig.5. : : : : : . 207 Drawing of a single quartz individual . : : : . } . 208 Map of South Wales Coal-field . : : : : : ‘ ee Locality map of New Zealand . : : ; é : 2 . 244 Sections of Monte Viso and Rocciamelone . : i : : . 251 Mandible of Nautilus pompilius . ? ; : : 4 : . 261 Mandible of Nawtilus (Rhyncholithes butleri, n.sp.) sp. . : 5 GR Diagram of distribution of temperature in depth . : : : . 269 Sketch-map of crystalline rock-areas, Northern Piémont : : . 3806 Stripped fossil denudation plain . : : : : : : _ BG Zocecia of three Bryozoa from Norseman Limestone . : ‘ 3 BRL Trogonthertum from Copford : ; 5 ; : : ; a BB Section of brick-pit, Barnwell Station . : ; : : ; . 841
Sketch-plan of Lanzo Valleys, Grajan Alps. : : 5 : . 3849
vill List of Illustrations in the Text.
Section of liparite exposure . : : 5 : Section showing outcrop of the Coral Rag and Ampthill Clay Sketch-map of crystalline massif, Savona
Sections of crystalline massif, Savona .
The Kegworth footprint
Map of Voltri Group, Western Liguria
Map and sections of ophiolithic groups, Eastern Liguria Map of ophiolithic groups, Hastern Liguria .
Dallina floridana, Pourtales
Section of coral, New Guinea
Small glacier, showing the snow-line
Diagram of earth’s areas mapped in 1860 and 1916
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I. ORIGINAL ARTICLES. Page . IIL. Reviews. Page an a Mounted Skeleton of a Dr. A. Keith’s Antiquity of Man... 32 ae ‘Gazelle-Camel’. By ©. W. Prehistoric Archeology... ... ... B4= ANDREWS, D.Sc.,F.R.S. (Pl. 1.) 1 | Pleistocene Mammals, Iowa... 35 - Trail and Underplight. By R. M. Coal-measure Amphibia 35 DEELEY, M-inst.C.E., F.G.S. New York State Museum 36 AWith 2iVext-fioures:)< 7. 41. 2 The Trilobite Harpes 36 _ Axinite Veins in Penmaenmawr The Edrioasteroidea 37 poor. ie OC. SARGENT, H. A. Allen : Cretaceous Mollusca 37 z F.G.S. 5 | Professor J. Barrell: Isostasy, etc. 38 : ee Hoeniation:. in tae Alps of. Delta Deposits of Nile aes ee Piémont, Dauphiné, and Savoy. Doelter’s Mineralogy 39 By C. 8. Du RICHE PRELLER, A Russian Meteorite 40 M.A., Ph.D., F.G.S., F.BR.S.E. Brief Notices : Mineral Production ie (With 2 Page-illustrations.) ... 7 of India—Porosity of Rocks, Sw gts St. Bees Sandstone of West Karroo—Brighton’s Lost River.. 40 Cumberland. By StipNEY MEL- IV. REPORTS AND PROCEEDINGS, -. MORE. (With 2 Text-figures.)... 17 | Geological Society of Glasgow Al Brachiopod Morphology. By J. Geological Society of London— - WILFRID JACKSON, F.G.S. ... 21 November 17, 1915 : 42 - Glacier Lake Channels. By Pyro- December 1 . : Ad fessor PERCY Fry KENDALL 26 | Mineralogical Society 44 ees : V. CORRESPONDENCE. It. Novices oF Memoirs. Bernard Smith, M.A. ... .. 45 _ Ordovician, Cader Idris. By A. H. Professor T. G. Bonney, M.A., D.Sc. 47- - Cox and A. K. Wells... 30 | Dr. M. C. Stopes oe 47 Corrosive Brines, Manitoba. By VI. OBITUARY. Professor ‘R. C. Wallace, M.A 31 | Dr. Arthur Vaughan, M.A. 48
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THE
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MENV. SERIES, | DECADE: Vic .VOLe. Ik No. L—JANUARY, 1916.
ORIGINAL ARTICIES.-.
——_@—__—_
I.—Nore on a Mountep Sxeteton oF a ‘Gazeétir-CameL’, STENOMYLUS HITCHCOCK, Loomis.
By C. W. ANDREWS, D.Sc., F.R.S., British Museum (Natural History). (PLATE I.) (Published by permission of the Trustees of the British Museum.)
\HERE has recently been exhibited in the Gallery of Fossil Mammals at the Natural History Museum a restored skeleton of Stenomylus hitchcocki, Loomis, a ‘gazelle-camel’ from the Lower Miocene of Nebraska. ‘his specimen (M 10969), which has been mounted in relief by Mr. L. EH. Parsons, jun., includes portions of the skeletons of two individuals, but much of the dorsal region of the vertebral column and the ribs have been restored in plaster. The remains are from the Lower Harrison Beds (Lower Miocene) near Agate Springs, Co. Nebraska, where upwards of forty skeletons were edllected in a small area. Many were complete and lay in such a position that they are believed to be the remains of a herd overtaken by floods and drowned.
Stenomylus was an extremely slender gazelle-like animal, differing widely from the usual conception of a camel. Its canines and first
premolars are incisiform, the molars low-crowned. The neck and _ limbs are slender and much elongated, and the metapodials are not yet united to form cannon-bones. This type of camel seems to have been confined to the Lower Miocene of North America.
The history of the sub-order Tylopoda (Camels) is a remarkable one. At the present day it is represented by one family only, the Camelide, and of this there are only two genera, one, Camelus, confined to Central Asia, the other, Auchenia, to the westernmost and southernmost parts of South America. When a group is thus represented by a few widely separated forms it may usually be assumed that it is the remnant of a formerly much more extensive assemblage which attained its maximum development in some region from which the few surviving forms have been derived. In the case of the Tylopoda this region was North America, where in the Tertiary period the group attained a great variety of form and where it survived in considerable numbers even to the Middle Pleistocene. During the Pliocene representatives had migrated into Asia and South America, and it is curious that although camels and llamas coexisted in North America no true camels reached South America and no llamas passed into Asia. This may perhaps have been because the camels, being
DECADE VI.—VOL III.—NO. I. 1
2 R. M. Deeley—Trail and Underplight.
more tolerant of cold, were alone able to pass into North-Eastern Asia, while the llamas of the time were better fitted to pass through the 'ropics to South America, where fossil forms have been found in Ecuador and Brazil. In the later Pleistocene the group became totally extinct in North America, hence its peculiar discontinuous distribution at the present day.
The earliest genus that can with certainty be referred to the Tylopoda is Protylopus from the Upper Eocene (Uinta). This genus includes animals about the size of a hare, in which the full dentition of 44 teeth was present, the bones of the fore-arm were separate, the fibula was complete, and there were four functional digits in each foot. In the White River Beds (Lower Oligocene) the genus Poébrotherium is represented by several species, some of which attained the size of a sheep. In this genus also the full dentition was present, but the selenodont molars were becoming high-crowned, the fibula was incomplete, and there were only two functional digits in each foot, although remnants of the others persisted. Up to this stage, according to Professor W. B. Scott, only one phylum is traceable, but in the Lower Miocene the group gives rise to two side branches, one, the gazelle-camels, of which Stenomylus is a representative, and the other, the curious giraffe-camels, which, as their name implies, possessed very long neck and limbs and probably browsed on trees like giraffes. The earlier (Lower Miocene) form Oxydactylus was much smaller than the later Alticamelus, and its neck and limbs were less elongated. The grazing camels, which may be regarded as the main stock of the group, possessed selenodont molars with increasingly high crowns, and in the later forms both in this group and in the giraffe- camels the metapodials fuse to form cannon-bones, the bones of the fore-arm unite, and the fibula is greatly reduced. Procamedus of the Upper Miocene of North America seems to represent approximately the common ancestor of camels and llamas. The earliest members of the sub-order yet found in the Old World are from the Lower Pliocene of the Siwalik Hills; other forms existed in the late Pleistocene and perhaps in Neolithic times in Northern Africa. In Europe remains of Pleistocene camels have been found in Southern Russia and Rumania.
IJ.—Trait anp UNDERPLIGHT. By R. M. DEELEY, M. Inst.C.E., F.G.8.
{J\HE peculiar features presented by the upper or land-surface I portions of some deposits, or rather those portions of certain deposits which are now, or have been in times past, land-surfaces, have engaged the attention of many geologists. Most of those who have studied them are satisfied that some features which they often show are not now being produced in this country, and they are attributed by many observers to the action of different climatic conditions to those which at present exist.
The form of disturbed surface deposit to which I particularly refer
R. M. Deeley—Traul and Underplight. 3
was called Trail and Underplight by Spurrel.' It would appear that many of the disturbances which have been produced in drift and - other deposits by the passage of ice over them are not of the same nature as those which occur in Underplight. Boulder-clays, for example, are often kneaded into the soft rocks upon which they rest, and thick deposits of sand and gravel have been disturbed greatly by ice which has passed over or been pressed into them. Disturbances of this nature have been described by Boswell? as occurring in the Suffolk Valleys. They affect Chalk, Thanet Beds, Reading Beds, London Clay, Crag, and glacial beds alike. In this area the trend of the summits and troughs of the folds, and other phenomena, indicate that the contorting force acted down the valleys, and the features noted are such as could not be produced by slip down the valley sides.
I have described and figured * the nature of the disturbances in the gravels, sands, ete., of the Trent Basin, which, from the strike of the ridges and troughs, show that they were due, like those described by Boswell, to forces acting down the main valleys. Such disturbances often present some of the features shown by Trail and Underplight, but, although this is the case, they do not appear to be of this nature.
Fie. 1.—T, Trail; UP, Underplight.
Osmond Fisher‘ noted the surface feature we are considering very carefully ; but was of opinion that the phenomena resulted from the infilling of drainage channels with rainwash and stones, combined with flow of the surface deposits. Such infilled channels certainly occur, and may be seen in the brickearth pits at Erith ; but whether they are washouts produced by floods or prehistoric infilled game pits it is not always easy to make out.
In the paper already mentioned Spurrel deals with the question of the formation and nature of Trail and Underplight in some detail. According to him a typical section shows (1) vegetable soil, (2) rain warp, (3) Trail, and (4) Underplight. The vegetable soil is to a large extent the result of the activity of earth-worms as described by Charles Darwin. The rain warp, an unstratified more or less sandy clay with pebbles, varies in thickness from a few inches to several feet. The Trail generally consists of a more or less sandy clay with pebbles, and fills the troughs in the Underplight. The Underplight is the soft rock on which the Trail rests, and has been contorted so as to form irregular pits or troughs in which the Trail
1 A Sketch of the History of the Rivers and Denudation of West Kent, etc. 2 Q.J.G.S., vol. lxix, pp. 581-618, 1913.
3 Thid., vol. xlvi, pp. 437-79, 1886.
4 Thid., vol. xxii, pp. 553-65, 1866.
4 R. M. Deeley—Traivl and Underplight.
rests. The contorted nature of the Underplight is not of a character to suggest that the troughs are eroded hollows as Fisher supposed.
Fig. 1 is a copy of Spurrel’s section xii, plate i. Here the surface flow is as shown by the arrow. There are two well-marked layers of Trail (T’), the upper layer of Trail resting upon an Underplight of rainwash (UP), whilst the lower Trail rests upon an Underplight of brickearth (UP). ‘he Trail has the appearance of being due to the sinking of beds of heavy clayey gravel and sand into lighter beds of sandy clay. Whilst this sinking of the upper bed was taking place the whole surface was flowing very slowly in the direction of the arrow, the upper surface moving farthest down the slope. Indeed, the phenomenon is one which we should expect to find in a fluid of high viscosity rather than in a plastic one such as clay.
It is very generally agreed that Trail and Underplight are not now forming in this country, and that although beds of heavy sand or gravel may be now at times spread over beds of lighter clay by surface floods, the plastic nature of the clay prevents the heavier gravel from sinking into it. However, if the clay were wet and were alternately frozen and thawed, then for a short time after each thaw the clay, brickearth, silt, loam, or soft chalk would be in a slightly fluid condition, and any beds of superior gravity which rested upon them would sink into the deposit below. ,
Although some regard a plastic substance as being a highly viscous liquid, technically it is not. A plastic substance is a solid which, if not overloaded, will carry a load put upon it for an indefinite period without yielding. A highly viscous liquid, however, yields slowly. under any load, however small, and yields the more rapidly the greater the load (stress). Thus, if one stone be placed upon a piece of clay or soft plasticene, and another stone be placed upon a piece of hard brittle pitch, after an interval of a few months the one stone will be found resting as it was placed upon the clay or plasticene, whilst the other stone will have sunk more or less deeply into the brittle pitch. The pitch is a very stiff liquid and the clay is a soft solid. Under the conditions of climate now existing in this country the ground is seldom very deeply frozen, and consequently the soft beds of clay or brickearth are almost continuously in the plastic condition, and heavy material in or upon them cannot sink. But when the ground is annually deeply frozen and contains much moisture, for a short time after each thaw the thawed clay or brick- earth virtually becomes a liquid for a time and allows heavier materials in or resting upon it to sink some distance.
It is clear that if the process of the sinking of a layer of gravel and sand into a lighter layer of soft clay went on long enough, the gravel and sand would eventually all collect beneath a layer of clay at the level to which the thaw penetrated each summer; indeed, some sections show beds of gravelly clay resting upon and covered by loam, clay, or brickearth, oblique streaks of small stones remaining in the upper deposit.
No doubt there is generally a slow bodily movement of hills composed of plastic clays, ete. Such movements, however, are not of the nature of fluid movement (viscous flow). They. probably
H. C. Sargent—Axinite Veins, Penmaenmawr. 5
result from the flexing of the whole crust, resulting from the tidal action of the moon and from undue stresses arising from denudation. In the construction of the Panama Canal movement of the beds took place to a large extent.
But would “the settlement of a high gravity material into one of lower gravity produce results resembling Trail and Underplight ? That such would be the case I have attempted to demonstrate in the following manner :—Into a shallow cardboard box a layer of pitch about 1 inch thick was poured. Upon this, when cold, a layer of sealing-wax mixed with fine and coarse sand was run. When the whole was quite cold the cardboard box was slung beneath an inverted incandescent gas burner. In this way the wax and pitch were slowly heated from above downwards and the viscosity reduced. Under these conditions the weighted wax slowly sank in irregular patches into the black pitch, which rose up around the descending wax. After the lapse of ten hours the cardboard box was removed and its contents allowed to cool, and when quite cool the cake of
Fic. 2.—W, Wax; P, Pitch. wax and pitch was broken through, Fig. 2 showing a trace along one of the lines of fracture. It will be seen that the forms assumed by the heavy wax closely resemble Trail, whilst the pitch assumes the form of Underplight. Close examination shows that the coarse grains of sand, especially near the sides of the descending masses of sealing-wax, stand i in a vertical position as do the stones in Trail.
The above experiment does not, of course, prove that Trail and ‘Underplight were actually formed in the manner assumed; but it does show that.a bed of sand or gravel spread over a bed of soft clay, if rendered slightly fluid at times by repeated thawing, would most probably settle into a form which would resemble Trail and Underplight.
One of the points of interest is that deep freezing and thawing of the soil is required to produce the effect. We are dealing, therefore, not merely with conditions which are interesting as being a probable explanation of the method of the formation of Trail and Underplight, but with features which (in areas where soft clays occur and signs of true glaciations are absent) should enable us to ascertain when cold periods have occurred.
JIT.— Axinire Veins In tHE PenMarnmawr PorpHygite. By H. C. SARGENT, F.G.S. N the course of a visit to North Wales last summer my friend Mr. Ivor E. Davies, of Penmaenmawr, called my attention to a mauve mineral, forming thin veins, in the intrusive porphyrite of
6 H. C. Sargent—Aainite Veins, Penmaenmauwr.
Penmaenmawr Mountain. The specimens containing the veins were not seen in place, but were collected from the waste-heaps of the Graig Lwyd Quarries, the most easterly of the large quarries that are making such deadly inroads into the heart of the mountain. Careful search on the waste-heaps enabled us to collect further specimens, and in some of these the mineral had built in fissures and cracks somewhat crowded, very sharp-edged crystals of tabular development.
I am indebted to the kindness of Dr. G. T. Prior, F.R.S., for the identification of the mineral in question as axinite. Several writers have made a special study of the Penmaenmawr veins,’ but none of them seems to have been aware of the occurrence of axinite in them, and a brief description of its habit and associations may therefore be not without interest.
The vein-specimens collected vary in width from 2 inches down- wards, but of this thickness the mauve axinite forms only an inner subsidiary vein, or veins, varying from half an inch down to a sixteenth in thickness. The other portion of the veins is of a light- grey colour, and is seen in thin sections to consist of axinite associated with a considerable proportion of quartz, the latter mostly in small irregular grains and clearly of secondary origin. The quartz some- times takes on crystal contours on the edge of the light-grey portion of the veins and the crystals then penetrate the subsidiary mauve veins. The mauve infilling would therefore appear to be a later product than the light-grey axinite.
The thin sharp-edged crystals developed in fissures and cracks are of a pale-brown colour, and their greatest dimension is about a quarter of an inch. Sometimes the mineral forms thin radiating blades nearly an inch in length. Thin sections of the material in the veins do not show crystal outlines, the growth of crystals being interfered with by crowding, but cleavage is often well marked—on m (110) according to Weinschenk?—and extinctions measured to the cleavage-traces have a maximum angle of 42°. Sections which are inert, or nearly so, between crossed nicols are, of course, normal, or nearly so, to an optic axis. Such sections, in convergent light, show only one bar, which bends very slightly on rotation of the stage, thus indicating the wide axial angle (2V=72°). The dispersion is very marked (p<v).
Axinite, a borosilicate of lime and alumina, with variable amounts of iron, magnesia, manganese, etc., is generally associated with calcareous sediments and igneous rocks rich in lime, within the contact-aureoles of granites; but that it is of pneumatolytic origin, and not a product of thermo-metamorphism, has been shown by Messrs. Barrow & Thomas.‘ Its frequent association with prehnite,
1 See, for instance, Waller, Midland Naturalist, 1885, p. 5; Teall, British Petrography, 1888, p. 275; Schaub, Newes Jahrbuch fiir Mimeralome, etc., Abh., pp. 108 et seq., 1905; Sargent, Gkou. MAG., Dec. VI, Vol. II, pp. 20-1, 1915.
2 Petrographic Methods, trans. Clark, 1912, p. 366.
3 Weinschenk, op. cit., p. 367.
4 ** On the occurrence of Metamorphic Minerals in Caleareous Rocks in the Bodmin and Camelford areas, Cornwall’’: Mineralogical Magazine, vol. xv, pp. 113-23, 1908.
Dr. Du Riche Preller—Permian in the Alps. 7
as at Bourg d’Oisans, has been noted by other writers. Here, too, the mineral so abundant in the green veins of Penmaenmawr, which Schaub has determined as prehnite,' is at times seen to be intimately associated with the axinite. It has a lower refractive index and higher birefringence than the latter, and where cleavage-traces are developed it extinguishes parallel thereto (001). A genetic relation- ship between the two minerals appears to be indicated.
In all the cases which I have seen recorded hitherto the gaseous boron-bearing emanations leading to the production of axinite have followed the intrusion of a granite magma. At Penmaenmawr the magma was of intermediate calc-alkalic character. It is assumed that here, too, the hot gases charged with boron-compounds reacted on the original lime-bearing minerals of the veins, releasing the silica and forming new combinations with the lime and other constituents, and that thus the secondary mineralization of the axinite veins was essentially effected. In the Cornish greenstones the production of axinite is usually accompanied by ‘‘one or more of the following minerals, pyroxene, epidote, hornblende, garnet, quartz, and felspar, while zoisite, zincblende, sphene, and fluor-spar are sometimes present’. With the exception of quartz, a soda-lime felspar, and a little epidote, none of these minerals has been observed in the axinite veins of Penmaenmawr.
The green and other veins, which are so abundant at Penmaenmawr and have been previously described, as mentioned above, consist predominantly of micropegmatite and orthoclase, with subordinate plagioclase, augite, ilmenite, biotite, and apatite. It may perhaps be assumed that the axinite veins, which appear to be of very limited distribution, were originally filled with predominantly basic material, rich in lime; and that this took place at some other period, probably earlier in the course of the intrusive episode, than that which saw the production of the more acid veins. Somewhat confirmatory of this suggestion is the fact that. in the same neighbourhood, viz. the most easterly Graig Lwyd Quarry, an interesting vein or patch was recently exposed, consisting essentially of calcite and tale, largely intergrown with each other.
1V.—Tue Permian Formation in THE Ars oF Primont, Davpgine, AND Savoy.
By C. S. Du RICHE PRELLER, M.A., Ph.D., M.I.H.E., F.G.S., F.R.S.E. . I. Inrropuctory.
N a recent paper on the Marble District of the Apuan Alps or Carrara Mountains*® I showed that the gneissose schists which form the nucleus of that range, and upon which rests the Triassic marmiferous formation, are, not of Archean, but, upon irrefutable paleontological evidence, of Paleozoic age, and that, upon equally
1 Neues Jahrbuch fiir Mineralogie, Abh., p. 110.
2 The Geology of the Country around Bodmin and St. Austell (Mem. Geol. Surv.), 1909, p. 53.
3 GEOL. MaG., December, 1915, pp. 554-65.
8 Dr. Du Riche Preller—-Permian in
conclusive lithological and stratigraphical evidence, they must be assigned to the later part of that period, that is, to the Lower Permian. The former conclusion was first arrived at in the course of the geological survey of the range by Lotti and Zaccagna and upon the paleontological authority of the late Professor Meneghini; the latter conclusion was chiefly the result of the striking analogy, first pointed out by Zaccagna, between the stratigraphical sequence and lithological characteristics of the Apuan Alps and the Montgioie range of the Maritime Alps which forms the divide between Southern Piemont and the Western Italian Riviera.
The geological survey of the Montgioie range, carried out in the eighties, was subsequently extended to a revisionary survey of the Italian side of the Cottian, Grajan, and Pennine Alps for the com- pletion of the new geological map of Italy then in course of prepara- tion and published in 1896; but the latter survey, by Zaccagna and Mattirolo, revealed such fundamental differences between the Italian interpretations and the existing maps of the French side of the Alps that it had, in its turn, to be extended to the French border districts. In the result Zaccagna’s conclusions, fortified by his experience in the Apuan and Maritime Alps, were fully confirmed, not only as regards the continuity of the Permian formation from the Maritime Alps to the Western Alps on the French side, but also in relation to the pre-Paleozoic formations, a great part of which was’ until then regarded by French geologists as of much more recent, that is, of later Mesozoic age.
Having visited the Piémontese, Dauphiné, and Savoy Alps on several oceasions, both then and more recently, I propose to succinctly review the main features of the Permian formation in the principal localities, and also to refer briefly to some of the other important points elucidated by the Italian revisionary survey on the French side of the Alps. (See sketch-map, p. 10, and plan and sections, p. 11.)
II. Tue Permian in tHe Maritime Axes.
As shown in the sketch-plan (Fig. 1, p. 11), the Italian Maritime Alps, embracing the Ligurian and the Montgioie ranges, extend from Savona west to the River Tanaro, and thence to the Col di Tenda, beyond which lie the Mercantour gneiss and granite massif and the Cottian Alps. The Montgioie range, in which the Permian formation reaches its maximum development, comprises in a length of about 50 kilom. between the Tanaro—an affluent of the Po—and the Col di Tenda road a remarkable series of rugged and peaked mountains
1 These surveys, accomplished in four consecutive short summer seasons, and embracing the Maritime and the whole of the Western Alps, including the Mont Blane massif on both sides, constituted on Zaccagna’s part a veritable tour de force, enhanced by his exhaustive reports in the Bollettino R. Com. Geol. d’Italia of 1887, pp. 346-417, and 1892, pp. 173-244 and 311-404, with maps and sections. He also compiled, with Issel and Mazzuoli, an excellent geological map 1 : 200,000 of the Ligurian and Maritime Alps for the Italian Alpine Club in 1887. The circular examination of the Mont Blanc massif was carried out by Zaccagna himself, while a section from the Arve (Chamounix) Valley across Mont Blane by the Col du Géant to the Dora Baltea (Aosta) Valley was taken by Mattirolo.
the Alps of Piémont and Savoy. 9
of an average elevation of 8,000 feet, separated by passes up to 8,000 feet above sea-level. The highest mountain is Montgioie, 2,630 metres altitude, situated practically in the centre, but both on the north and the south the crest-range is flanked by a parallel range of somewhat lower elevation.
The Permian formation occupies, in a width of about 40 kilometres, the greater part of the central and also of the northern subsidiary range, the declivities of both being deeply eroded by the Tanaro and its tributary torrents. On the east the formation thins out towards the hills above Savona, and on the west crosses the Stura Valley, whence it passes into Dauphiné. The southern subsidiary range comprises Monte Abisso, Monte Rocchetta (2,473 metres altitude), and some deposits south of Col di Tenda, as part of the Permian formation, but is chiefly composed of Triassic and Liassic strata bordering on a large area of Eocene albarese limestone and macigno sandstone which reaches to the Riviera seaboard of San Remo. Besides Rocchetta and Montgioie, the most remarkable Permian mountain is Monte Besimanda, 2,404 metres altitude, which is entirely composed of that formation and with its double-peaked summit is a conspicuous object as part of the northern subsidiary range, being situated about 20 kilometres south of Cuneo and 10 kilometres east of the Col di Tenda road. The Permian formation, overlying the Carboniferous, may be conveniently studied in the outcrops of those and other mountains, more especially in the deep and narrow valleys of the upper Tanaro and its affluents, one of the most interesting and accessible of which is that of the Negrone torrent on the southern flanks of Montgioie, where the sequence of strata can be distinctly traced on both sides. Another instructive locality is that of the ravines of the Bormida torrents east of the Tanaro and south of Monte Settepani, where the contact of the Carboniferous and the Permian is well exposed at several points.
Up to the ’eighties the principal authority on the Maritime and Western Italian Alps was Gastaldi, who, besides his well-known studies on the crystalline and pietra verde rocks and an unpublished map of the latter Alps, left a memoir on the former.’ He was at first disposed to class the gneissose schists of the Montgioie range with the Archean gneiss of the Western Alps; but the Montgioie schists, owing alike to their ‘“‘ deficient crystallinity” and to their strati- graphical location, presented so puzzling a phenomenon that, pending further definition, he designated them as of indeterminate age under the name of ‘ apenninite’, as being akin to the Apennines rather than to the Alps. As this formation does not extend east beyond the Savona hills, and is in no sense characteristic of the Apennines proper, the name was obviously a misnomer, and hence Zaccagna, who was the first to recognize its true stratigraphical position, chose the name of besimaudite, from Monte Besimauda already referred to, as typically representative of the gneissiform schist, which has its equivalent facies both in the Apuan and the Western Alps, and also in the so-called Suretta gneiss of the Spliigen Pass.
1 “ Fossili Paleozoici Alpi Marittime’’: Atti R. Acad. Lincei, 1877.
10 Dr. Du Riche Preller—Permian in
| Sketch Map of Permian Formation from Maritime Ups fo Montblanc. 1:2,c00000
ra) 20 +O 60 Kil
eet 28 lay Soa: dey @ 1% Cand 4G. Combin Mi. Cervir "a @ +@ nN “Bor *, LIP 6 anet
O° Th Blanc@ ag ee | S ae As ae Gel St Beyaass Mm Rose
wee aiey I Cowargire he
ye :
og [serge 33.66% tec. Panadtso 0) Ova
2
“Moubie ° 5 N.Isera f at ay f i & ; : < lod aite naga Ree ry AS Qorg ; rH a(t D § erty i "Ries o Tunor e NS; 3135 S l - » 1359 ‘ — x ry ae on & Ve. att s Po a Np \ Mm. Chee de gir . ny jay 9
6 Canes 2 5 ai an : As a aS +e ne Aye auene Mon Asove (7 3059 MPa 4 "Ot fer a ie 3) (973
mextantoun ** Xn dag ON Be P| 4 re altitudes m melted S wh vd =a eee oe Zon nes of. Archean Gneiss XGranite
wma Fermian Formation. **%x Fronlier. nee
the Alps of Piémont and Savoy. 11
THE PERMIAN FORMATION IN THE MARITIME ALPS.
—> ude, ee
my
Born =
247
a Dich elle, Eonar ea a ar
Fic. 1.—Sketch-plan. Scale 1 : 1,000,000. M= Miocene. P= Permian. Ho= Hocene. C= Carboniferous. L=Lias. CS =Cale-schist ) Nea
IMI Naais, G=Gneiss J
Fic. 2.—Section of Montgioie (2,631 m.), S. to N. Scale 1: 1,000,000. T, 1, m, u= Lower, Middle, and Upper Trias.
: “i Zi
\
Enel WIRED nee aa
if Anyemenge RSS
LZ; ii Ay} Wi Mid Fic. 3.—Section of Cime de Rochettee (2,476 m.), S. to N. x = porphyritic mass.
D. R, P. del.
12 _ Dr. Dw Riche Preller—Permian in
The Permian formation reaches a thickness of at least 1,000 metres, and rests directly and conformably upon the fossiliferous Carboniferous strata, which attain about half that visible depth and constitute the lowest zone of the Montgioie range. The latter strata are, as usual in the Alps, composed in the main of blackish carbonaceous and grey micaceous schists, graduating into talcose greenish cale- schists, which become felspathic and then pass into quartzose schist, which forms the base of the Permian formation. The Carboniferous age of the strata underlying the Permian, and consequently the Permian age of the besimaudite zone itself, was definitely established by fossils found in the Negrone Valley near Viozéne, on the southern flank of Montgioie, by Zaccagna, and determined by Professor Portis of Pisa. Soon afterwards this discovery was confirmed independently by Squinabol and by Mazzuoli, both of whom found indubitably Upper Carboniferous fossils in the Bormida valleys already mentioned, where the Carboniferous strata are, moreover, anthracitic.!
The distinguishing feature of the besimaudite zone, like that of the equivalent schists of the Apuan Alps, is its gneissiform character, but it also comprises, in upward progression, a variety of associated rocks. Thus, from a granular quartzose schist it passes into greenish- grey compact rock of porphyritic texture with large elongated felspar crystals up to 2 centimetres in length. Again it passes into nodulous gneissiform schist without felspar, or again into sericitic schist, and in places also assumes a granitoid structure, notably above Savona. There are also hornblende-bearing intercalations, simulating the aspect of pietra verde. In Monte Rocchetta occurs a large mass of reddish porphyritic quartzose rock with white mica crystals, which Zaccagna regards as intrusive porphyry, and which also occurs in Monte Abisso, close to the Col di Tenda Pass; but I am disposed to regard both these masses, which, moreover, lie in a zone, rather as Upper Permian, very similar to the red verrucano or sernifite of the Glarus Alps, a clastic rock which often has all the appearance of
porphyry. _ The besimaudite zone is directly and conformably overlain by, and graduates into, a coarse conglomerate with white and reddish pebbles in a greenish, taleose matrix. This conglomerate or ‘anagenite’ is of considerable depth in the Montgioie range, and also occurs sparsely in the same position in the Apuan Alps. It represents the Upper Permian or Verrucano formation, and marks a transition from the
latter to the Lower Trias. In my opinion, the porphyritic masses of
Monte Rocchetta and Abisso already mentioned form part of it. It graduates, in its turn, into the conformably overlying Triassic series of quartzite, grey subcrystalline limestone, and calcareous schists, and these are overlain by banks of blackish, brecciform, marmiferous limestone with white calcite crystals, which is quarried near Villanova, at the northern base of the range, and is conspicuous in
A. Portis, Boll. R. Com. Geol., vol. xviii, p. 417, 1887 ; L. Mazzuoli, ibid., p. 6; S. Squinabol, Giornale Scient. Genova, Fascic. Giugno, 1887. The survey of the Ligurian Alps eastward from the Montgioie range, surveyed by Zaccagna, was carried out concordantly by Mazzuoli and Issel, Boll. R. Com. Geol. 1884 et seq.
the Alps of Piémont and Savoy. 13
the columns and ornamental architecture of the churches and palaces of Turin. The Triassic series, about 400 metres in thickness, crowns Montgioie and most of the other principal mountains of the range, on the southern base of which occur also some Juraliassic and Cretaceous outcrops, followed by a large area of Kocene lime- and sandstone, while on the north it is bordered by an equally extensive area of Miocene marl and molasse.
Thus the stratigraphical sequence of the range, illustrated in the two typical parallel cross-sections of Montgioie and Rocchetta (p. 11, Figs. 2 and 3), exhibits a close analogy to that of the Apuan Alps from thé Permian formation upwards. In the Montgioie range the flexures are inclined to the west, where the strata abut unconformably against the gneiss and granite massif of Mercantour ; in both the Montgioie and the Apuan range there is considerable folding, but no faulting or unconformity, and their uniformity of age, sequence, and general lithological character is abundantly demonstrated.
IIT. Tar Permian in tae WEsTERN ALps.
From the Montgioie range the Permian formation extends in a westerly direction to the Cottian Alps, and thence continues N. and N.N.E. to the Grajan Alps and the base of Mont Blanc. As the limits of this paper do not admit of a detailed description of the different localities, suffice it to indicate briefly the alignment of this extension of the Permian zone.
1. In Dauphiné. From near Boves at the north-western extremity of the Montgioie range, the Permian, skirting the Monte Viso massif on the right and that of Mercantour on the left, crosses the Stura Valley, and from here forms an uninterrupted zone about 60 kilometres in length and 2 to 5 kilometres wide to the Ubbaye Valley and Mont Chambeyron (38,3888 metres altitude) on the Italo-French frontier. Thence it reappears further north on the south-eastern side of Briancon, near Mont Genévre, and, skirting the frontier, continues for about 15 kilometres to Mont Chaberton (3,135 metres), this zone being about 2 kilometres in width.’ ~
2. In Savoy. The next outcrop occurs about 20 kilometres north of the last point, near Modane, below the northern end of the Mont Cenis tunnel, in the Are Valley, at an altitude of about 1,000 metres, whence it extends in a belt 5 kilometres in average width to St. Bon, Bozel, and Champagny in the Doron Valley east of Moutiers.*
1 The Mont Genévre group and Mont Chaberton have been dealt with at length in the interesting papers respectively by Cole and Gregory, Q.J.G.S., 1890, p. 305 et seq., and by Davies & Gregory, ibid. 1894, p. 307 et seq.
2 Near Moutiers are the two geologically famous localities of Petit Coeur and Mont Jovet in the Tarantaise district of the Isére Valley. Near Petit Coeur, about 6 kilometres north of Moutiers, the long-debated phenomenon of a Carboniferous, fossiliferous stratum being wedged between two strata of Jurassic fossiliferous limestone was interpreted, among others by Lory, as due to a fault, whereas Zaccagna explained the Carboniferous strip more naturally as the remnant or denuded extremity of a synclinal fold, the other end of which appears in a somewhat larger outcrop at Hautecour, some 6 kilometres east of Moutiers. In Mont Jovet (2,303 metres), on the other hand, the puzzling feature was its being capped by a considerable mass of cale-schist with pietra
14 Dr. Du Riche Preller—Permian in
It then reappears—
3. In Northern Piémont above Courmayeur, at the foot of Mont Blane, in the two well-known mountains Chétif and La Saxe (2,343 and 2,358 metres), separated by the Dora Baltea, and again, some 5 kilometres lower down the Dora Valley, in the Pian d’Arp, an eminence near Pré St. Didier.
Throughout this more or less continuous belt from the Maritime Alps to Mont Blane the Permian exhibits the besimaudite and verrucano characteristics already described, and runs parallel with, and in normal sequence between, the Carboniferous and the Triassic series, so much so that the three zones, with the addition of a narrow Jurassic zone, all bifurcating at Col de Bonhomme, the south-western spur of Mount Bianc, form a belt, more or less interrupted by denudation, round that massif.
Of the Permian outcrops, those of Modane and Courmayeur are of special interest: (1) that of Modane, because Lory and other French geologists included it in their great zone of crystalline metamorphosed ‘Triassic schists, whereas its interposition between Carboniferous and Triassic—both fossiliferous—strata clearly proves its Permian age; and (2) that of Courmayeur, because Chétif and La Saxe were regarded as granitic spurs of the Mont Blanc massif,’ whereas Zaccagna recognized them as the northern extremity of a Permian synclinal fold, which is conformably overlain by the Triassic series, and whose southern extremity is the outcrop of Pian d’Arp near St. Didier, already mentioned. It appears again in the St. Mary Mountain near Aosta, some 20 kilometres down the Dora Valley.
In Savoy the Permian zone from the Arc Valley at Modane to the Doron Valley south-east of Moutiers has more recently been considerably enlarged by Termier, more especially in the Vanoise region and in the Doron Valley itself.2 In Dauphiné the crystalline schists of Mont Genévre near Briancon have also been assigned to the Permian, whereas this formation only skirts the western base of that group, and is overlain by dark, indubitably Triassic limestone corresponding to the grezzoni of the Apuan Alps, while the crystalline schists with their diabasic and serpentinous (pietra verde) intercalations are clearly Archeean.? verde or vert des Alpes intercalations, surrounded by a Triassic belt. The former outcrop was regarded by Bertrand as Liassic, while Professor Lory included it in his Triassic metamorphosed schistes lustrés, and lastly, Zaccagna recognized it as schistes lustrés but of Archean age, the pietra verde intercala- tions being conclusive evidence by analogy with Mont Genévre, Susa, etc. Professor Gregory, in his searching analysis of all the evidence (Q.J.G.S., 1896, pp. 1-16), concludes in favour of the pre-Carboniferous age of the Mont Jovet schists, viz. in the absence of the Lower Paleozoic, virtually in favour of their Archean age.
1 The Val Veni depression between these two mountains and the granite massif of Mont Blane is filled with Liassic limestone resting conformably against,the Permian of the former but unconformably against the latter.
2 ‘* Btude sur la constitution géologique du massif de la Vanoise’’: Bull. ‘Carte géol. France, vol. ii, No. 20, 1891.
3 A sketch-section of part of the Mont Genévre group is given in Professor
Bonney’s paper, ‘‘ Two Traverses of the Crystalline Rocks of the Alps’: Q.J.G.S., 1889, p. 80. The limestone at the western end is marked Jurassic, probably on the strength of Lory’s map as Lias compacte or calcawe Brianconnais. It is now included in the Trias.
the Alps of Prémont and Savoy. 15
TV. Tur PERMIAN IN RELATION TO ARCH#AN AND Mesozoic Scuists.
Intimately connected with the stratigraphical position of the Permian is the demarcation of the Archzan and Mesozoic schists. As is well known, both Elie de Beaumont in the French map (1860) and Sismonda in the Italian map (1862) of the Western Alps divided the crystalline rocks into two great zones—a lower one, comprising indiscriminately the Archean gneiss, and the Paleeozoic and Mesozoic series, as the ‘‘ metamorphosed Jurassic area’”’; and an upper one, embracing the Archean granite and all the pietra verde rocks, as intrusive and post-Jurassic. The later maps of Lory and Favre of the French, and of Gastaldi of the Italian side, to some extent disentangled that strange confusion: Lory and Favre by assigning the gneiss, granite, and the ‘‘ vert des Alpes” to the Archean and all the mica- and cale-schists indiscriminately to the Trias as “ schistes lustrés’’, while Gastaldi separated all the pietra verde rocks into. a zone per se as overlying the primitive gneiss and granite zone, and labelled it and the mica- and cale-schists as crystalline rocks, more recent, but pre-Paleozoic. The Permian did not figure in any of those maps.
Such was the position in the ’eighties when Zaccagna’s revisionary survey showed those more or less arbitrary classifications to be obsolete and untenable. Accordingly he defined the Archzean as composed of two zones—a lower, comprising exclusively the primitive gneiss and granite rocks, and an upper, embracing the mica-schists (schistes lustrés) and the small-grained tabular gneiss; the calc-schists and erystalline limestone; and the great masses of pietra verde as a con- temporaneous part.! From the Carboniferous formation, till then held - to be the only representative of the Paleozoic in the Maritime and Western Alps, he separated the Permian besimaudite and verrucano zone directly overlain by the indubitably Triassic series in which he included Lory’s ‘‘Lias compacte”’ or Brianconnais limestone. This clear definition of the Lower and Upper Archean, the Upper Paleozoic, and the Lower Mesozoic formations harmonized the two sides of the Western Alps, and was embodied in the new geological map of Italy of 1896, a preliminary sketch of the earlier results in the Maritime and Cottian Alps having been already exhibited at the Berlin Geological Congress of 1885. These were largely, if with variations, adopted by Vasseur and Carez in their geological map of France of the same year.’ Zaccagna’s conclusions were thus, in the main, signally vindicated.
1 The small-grained tabular gneiss (gneiss minuto tabulare) is extensively quarried in the Susa, Chisone, and Pellice Valleys for building purposes in Turin.
2 Vasseur and Carez assign the crystalline schists west of Monte Viso on the Italian side to the Paleozoic (Cambrian), for which, however, there is no warrant, the absence of the Lower Paleozoic in the Western Alps being, on the contrary, an important feature as marking a long interval of erosion which led up to the Carboniferous formation, composed of the sedimentary and calcareous products of that erosion in which were engulfed the vast débris-accumulations of a luxuriant vegetation. The Archran age of the crystalline schists was, after Zaccagna’s publication in 1885, affirmed also by Professor Bonney (1886 and 1889), in relation to the Alps generally.
16 Dr. Du Riche Preller—Permian in the. Alps.
In so far as the degree of crystallinity, being the effect of metamorphism under pressure and high temperature, is a test of age, the Archean highly crystalline schists differ from the gneissiform Permian schists as much as do the latter from the still less crystalline Triassic schists, e.g. those of the Apuan Alps as part of the marmiferous zone, albeit both those younger schists often simulate a gneissose aspect. As regards the Archean schists, the presence of igneous rocks, whether primary or altered, is, of course, no absolute criterion of age, but in Piémont the enormous pietra verde masses of Monte Viso, of the Dora Riparia Valley, and of Val d’ Aosta are by alternation, eraduation, and lenticular intercalations, or again as irregular, obviously eruptive deposits, so closely associated with the mica- and cale-schists that their inclusion in the Upper Archean zone appears perfectly legitimate. As in the younger schist-formations, so also in that Archean zone the mica-schists always form the lower part of the zone, gradually passing into calc-schists which predominate in the upper part, with intercalations of saccharoidal limestone, quarried e.g. in the Susa Valley. It is with the upper parts of the mica- and the lower parts of the calc-schists that the pietra verde masses are more especially associated, and the intermediate position of the latter therefore points to their original subaqueous or superficial eruption in the corresponding period.'
VY. Conctustion.
In the necessarily small sketch-plan (p. 11, Fig. 1) I have traced the Permian zone from the Ligurian Alps near Savona through Southern Piémont, Dauphiné, and Savoy to Mont Blanc, a distance of 250 kilometres. It is seen that the curved alignment of that zone, which would equally apply to the concomitant Carboniferous and Triassic zones, runs, in the main, between and parallel to the two great primitive gneiss and granite belts indicated by dotted lines, the outer belt comprising the Mont Blanc massif and the Pelvoux group in Dauphiné, while the inner, more continuous one extends from Monte Rosa to Gran Paradiso and Mercantour in Southern Piémont.’ A third, smaller, but continuous inner belt may be said to lie between the Dora Riparia and the Maira Valleys, with Monte Viso midway
1 In Piémont alone the crystalline schists, lying between the Mercantour massif in the south and Monte Rosa in the north, cover an area of 200 by 30 kilometres, or roughly 2,400 square miles, of which the three principal pietra verde masses represent about one-fifth. These masses are all composed ° of basie roeks, more especially of diorite, diabase, gabbro, serpentinous and hornblendic rocks. The white marble of Susa is, as shown above, Archean, in contrast to the Triassic marble of the Apuan Alps, but both attest the process of the deposition of coarse calcareous material being followed by that of gradually finer to very fine material purified by solution and precipitation. The majestic triumphal arch at Susa shows that the marble of that locality, as that of Carrara, was quarried already by the Romans. Similar saccharoidal limestone intercalations are also worked in the Pellice, Upper Po, and Varaita Valleys. I propose to refer to these and the pietra verde areas, as also to Franchi’s recent divergent views as to their age, in a subsequent paper.
2 GC. Diener outlines a similar series of belts in his Gebwugsbau der Westalpen, 1891, but embraces in his generalizations the entire ¢hain of the Alps.
Sidney Melmore—The St. Bees Sandstone. 1%
but outside the western edge, albeit this third belt forms more obviously part of the second one.
The surface-level of the Permian zone varies between 2,000 and 1,000 metres altitude, the highest being at Montgioie and Chétif (Courmayeur) and the lowest near Modane and in the Doron Valley, while the parallel Archean zones vary in altitude between 4,000 and 3,000 metres. Itis therefore obvious that the Permian and concomitant zones must have been deposited in a longitudinal trough at a time when the Archean groups had already experienced a first partial raising, followed by a long period of erosion in the Lower Paleozoic interval. The marked unconformity at the points of contact between the Archean and the Paleozoic and Mesozoic formations warrants the same inference of a long intervening period of erosion. A further uprise, which also affected the secondary formations, appears, on similar grounds of unconformable superposition, to have taken place in post- Liassic,! and a third occurred in Miocene times, which last-named movement, proceeding, like the preceding ones, mainly in a radial sense from the south-east, viz. from the Mediterranean, probably imparted to the. Maritime and the Western Alps, as also to the Ligurian and Apuan ranges, their present general alignment and configuration.
The initial emergence of the Montgioie and Apuan ranges as ellipsoidal groups probably occurred before that of the Apennines; but it 1s during the third and last great movement that the final uprise of the Permian schists, already more or less subjected to metamorphism and overlain by the younger formations, must have taken place in the Apuan Alps as the nucleus of that range, and as its average surface- level of about 1,500 metres above the sea is the same as that of the . analogous zone in the Maritime and Western Alps, it follows that the Permian formation in all the three ranges must have been raised to its present level simultaneously in Miocene times.
V.—A CuHemican Examination or tHE Sr. Brees Sanpsrone oF West CUMBERLAND. By SIDNEY MELMORE. {J\HE following analyses were made to ascertain the magnitude of local variations in the St. Bees Sandstone of West Cumberland. It will be convenient for this purpose to consider the district as follows :— : _ The area south of St. Bees, as far as Calder Bridge. The area north of Maryport, as far as Wigton.
1. THe area sour or Sr. Buss. In view of its basin-shaped character, the observed dips in this area vary considerably in value and direction. On the whole, however, there is a constant dip to the south.
1 Of this post-Liassic uprise, followed by a period of erosion, evidence is afforded by a general and marked discordance between the strata of the Upper Lias and the Tithonian, and, again, between the Neocomian and Senonian both in the Western and in the Apuan Alps.
DECADE VI.—VOL. IlI.—NO. I. 2
18 Sidney Melmore—The St. Bees Sandstone.
The general character of the sandstone is so well known as to need Under the microscope, specimens from
no further description here.
this area exhibit a few cases of secondary deposition of silica on quartz. The average thickness of these secondary layers is about 0°02 mm. :
West Newton xe x Jn Aspatria |° Maryport ty Flaiston : NN
Gos forth
Fic. 1.—Map of West Cumberland, showing localities mentioned in the text, with the observed dips. .
Samples of this sandstone were taken from St. Bees Head, a quarry near the village of St. Bees on the road to Egremont, a quarry near
Whinseales, Egremont, and from a quarry at Calder Abbey, near Full analyses were made of the samples from
Calder Bridge. St. Bees Head and Calder Abbey as representing the northern and southern portions of the area respectively.
Sidney Melmore—The St. Bees Sandstone. 19
The results are as follows :—
Ile iste
SiQ2. : ; i; A 83-99 85-96 Aly O3 5 , 5 ; 8-37 6-93 Fes O3 3 j 5 ; 1-61 1-36 He On mae. : i F none none Mn O2 4 R i ‘ none , none CaO. } P : : 0-49 _ 0-49 MgO i b : é 0-26 0-11 KO. ; , d ; 3-412 2-844 Naz O t : : ‘ 1-253 0-70 CQ.. : ; P 0-026 0-026 Hz» O (combined) F : 1-11 0-723 Sulphuric acid (S Os) : 0-31 0-32
100-831 99-463
I. St. Bees Head. II. Quarry at Calder Abbey. 2h
CA %, % &, Age We,
Combined. Weter —— : Sulphuric Acid ---------
Fic. 2.
The amount of combined water in the samples from St. Bees Quarry and the quarry at Whinscales was also determined, as also the iron at the latter place. The percentage of combined water and sulphuric acid are stated graphically in Fig. 2, as by this means the variations are more easily seen. The amount of ferric oxide is fairly constant, but shows a slight increase towards the northern end of the basin. The total alkalis show a marked increase in this direction.
2. THe AREA NoRTH oF Maryport. The remarks on the tectonics of the southern area apply also to this northern basin, but the constant dip is to the north. Samples were taken from quarries on the coast at Maryport, from a quarry at Hayton, from the West Newton Quarries, and from a quarry at Red Dial near Wigton. Fewer cases of secondary silica were noticed in the specimens from this basin, but when they occurred they were of the same order of magnitude as those in the southern basin. The amount of combined water was determined in the samples from Hayton and Wigton. The value of the combined water at Maryport is somewhat less than that of St. Bees, but it rises steadily to a maximum near West Newton, and then begins to decrease.
20 Sidney Melmore—The St. Bees Sandstone.
Full analyses were made of the Maryport and West Newton samples; the results are :—
Ii. Vs
SiQ2. ; , ‘ : 86-57 84-58 Aly Os , : : : 6-50 7-21 Fes O3 : : : , 1-92 - 2-05 FeO. : ; ‘ none none Mn O2 ni ; 5 i none none CaO. ; : : ; 0:57 1-40 MgO : : : : 0-083 0-098 K,0O. 5 : : : 1-618 1-376 Nag O : ; : j 0-574 0-392 COQ.. : 0-078 none HO (combined) ; i 1-042 1:72 Sulphuric acid {S Os) : 0-285 0-345
99-240 99-171
III. Sample from Maryport. IV. Sample from West Newton Quarries.
The percentage of ferric oxide continues to increase from the value found at St. Bees till it also reaches a maximum near West Newton, and then decreases in value. The percentage of S O, rises slightly in a northerly direction, its amount, however, being practically the same . for both basins. The total alkalis gradually decrease in the same direction.
Conctusions.
Considering each basin separately, all the localities where samples of sandstone were taken lie practically along the strike of the rock. The percentage of constituents found in these samples are therefore functions of the same geological horizon, and differ among themselves by virtue of their representing samples taken from different points of this horizon. The results therefore show superficial variations, rather than variations in geological time. It is well known that the process of kaolinization is accompanied by the formation of combined water, and this water 1s produced quantitatively in proportion to the kaolin. The degree of kaolinization can therefore be estimated with considerable accuracy by determining the amount of combined water in any sample of sandstone and correcting the value found for the presence of such other hydrated compounds as gypsum (Mackie, Trans. Edin. Geol. Soc., vol. vii, p. 454, 1899).
In the present connexion, the values of combined water plotted are uncorrected for combined water in CaS O,.2H,0, as the amount of calcium sulphate present in the seudeband is practically constant. Any alteration in the shape of the curve would be very slight if such a correction were applied. The substances whose presence is essential to kaolinization are water and carbon dioxide.
In sea-water the amount of dissolved oxygen varies from about 1 to 3 c.c. per litre, and the amount of carbon dioxide from 2 to nearly 40 c.c. per litre. The gaseous contents of sea-water increases with the depth to about 2,000 feet, below which depth the water contains scarcely any dissolved gases.
Assuming kaolinization to have proceeded under these conditions
J. Wd ackson—Brachiopod Morphology. sli
below the surface of the sea, and to have given rise to the amount of combined water found in the different samples of sandstone, we can arrive at the comparative depth of the various points in the basin where analyses have been made.
A section through the St. Bees basin from Calder Abbey to St. Bees will thus show a maximum depth at a point almost midway between St. Bees and Whinscales, the depth decreasing north and south.
Similarly, in the northern basin the maximum depth is attained a little north of West Newton, and decreases more rapidly to the south than to the north. Thus both basins were steeper at their southern extremity than at their northern.
The depth of the basin at Maryport was not very great ; in fact, we have evidence in the form of ripple-marks of littoral conditions at this place.
VI. —Bnracuiopop MorrHotocy: Norrs ann Comments on Dr. J. Auttan THomson’s PAreErs. By J. WILFRID JACKSON, F.G.S., Assistant Keeper, Manchester Museum.
)\ROM a long and careful study of the Brachiopoda I am led to offer some observations upon the two recently published papers by Dr. J. Allan Thomson which have appeared in this Magazine.} In the case of Dallina I cannot agree with Dr. Thomson regarding the type of folding. He considers D. septigera (the genotype) and D. raphaelis as dorsally biplicate, D. floridana as dorsally uniplicate. Now dorsal biplication is brought about by the dorsal sulcus being superimposed upon a single dorsal fold. In D. septigera, as well as in D. floridana, a broad ventral sulcus is superimposed upon a dominant ventral fold ; these two species, therefore, are, in my opinion, ventrally biplicate (as in Magellania flavescens and some others).
This confusion of folding has led Thomson to question the generic position of Zerebratula grayt, Dav., which was also referred to Dallina by Beecher.? This is a ventrally uniplicate species with alternate multicostation, and according to Thomson cannot belong to Dallina. He further states that ‘‘ there seems to be no difficulty in referring it to Magellania, as it apparently possesses the Magellaniform hinge- plate and cardinal process”. ‘There is some mistake here; the hinge-plate is not Magellaniform. Davidson’s figure ? is misleading. There is no hinge-plate such as occurs in the genotype of Magellania (I. flavescens). A mesial septum is present, extending from about the middle of the dorsal valve to near the apex, where it merges with slight bifurcation into a thick deposit, on the floor of the valve. _ From each side of this deposit the dental sockets and crural bases arise ; the cardinal process is transverse and weak. Apart from this
* “Brachiopod Morphology: Types of Folding in the Terebratulacea,’’ GEOL. Mac., Dec.- VI, Vol. II, February, 1915,-pp. 71-6; ‘‘ The Genera of Recent and Tertiary Rhynchonellids, ” ibid., September, 1915, pp. 387-92.
2 “* Revision of the Families of the Loop- “bearing Brachiopoda » and ‘‘ The
Development of Terebratalia obsoleta, Dall’?: Trans. Conn. Acad. Arts and Sei. -, 1x, pp. 376-99, pls. i, ii, 1893. aes Monograph of Recent Brachiopoda’’: Trans. Linn. Soc. London ;
ae (2), iv, pl. x, fig. 3, 1886-8.
22 Dey ian ackson—Brachiopod Morphology.
T. grayi cannot be referred to Magellania, or even to Dallina, on account of the ventral valve possessing dental plates in the form of strong buttresses with a small recess behind each. Dental plates are entirely absent from Magellania throughout life, and also from Dallina septigera and D. floridana, so far as the adult stages are concerned, but according to Fischer & Oehlert! the teeth of the ventral valve in D. septigera are supported in a young state by dental plates. These become attenuated with age and disappear entirely in the adult. TZ. grayi, therefore, is in need of a new generic name, as it cannot be referred to Zerebratalia even, on account of the loop being in a higher stage of development. ‘The name Zhomsonia, therefore, is now proposed for this form. ;
Let us now turn to Zerebratalia. This genus was founded by Beecher? on Terebratula transversa, G. B. Sowerby, a ventrally uniplicate shell, but, as Thomson points out, the actual species on which Beecher established a different ontogenetic series from that of Terebratella s.str. was Terebratella obsoleta, Dall.
Thomson considers this latter species to be a dorsally uniplicate form, and on this account creates a new genus—Dallinella—tfor its — reception. Beecher’s outline drawing of 7. obsoleta* is very misleading, and gives a very erroneous idea of the type of folding. Dall’s figure * is also of little service as it is only a dorsal view, but his description is very clear. I possess a specimen which agrees exactly with Dall’s description, and shows the true folding to be undoubtedly ventrally biplicate. ‘he anterior margin of the shell has much. the same appearance as in some specimens of Magellania flavescens.© The teeth of the ventral valve are supported by dental plates which are rather more definite than in Zerebratalia transversa and Thomsonia grayt.® In the dorsal valve the cardinalia is of the same weak character as in the two species just mentioned. The species, therefore, seems to me to be rightly placed in the genus Zerebratalia.
Thomson further suggests that 7. transversa, Sow., and 7’ coreantca, Adams & Reeve, are true Zerebratella, and if so Terebratalia becomes a synonym of Torebratella.
T. coreanica agrees with ZT. transversa and Thomsonia grayi in having the same type of dental plates and weak cardinalia, except that the cardinal process is somewhat more definite. Like Thomsonia grayt there is a callous deposit in the umbonal area. This species and 7. ¢ransversa cannot, therefore, be separated from the genus Terebratalia.
Such structural features as dental plates are, in my opinion, worthy of more consideration than has been given them in the identification and description of species. They are not only helpful
1 Hxpéd. Scient. du ‘‘ Travailleur’’ et du ‘‘ Talisman ’’, 1880-3, Brachio- podes, Paris, 1891.
2 Op. cit., p. 382.
3 Op. cit., pl. ii, figs. 6-9.
4 Proc. U.S. Nat. Mus., xvii, pp. 726-7, pl. xxx, fig. 7, 1895.
5 See Davidson, op. cit., pl. vii, figs. 6b, 10.
6 The dental plates in both these are very similar, and appear to have been overlooked in descriptions of the species.
J. W. Jackson—Brachiopod Morphology. 23
in defining genera, but their presence or absence is also an important
character separating the two sub-families Magellaninee and Dallinine.
' They appear to be entirely absent from the Magellanine, but are always present in the true Dallinine, even in fossil ; genera referred to this group.
The generic position of Zerebratula spitzbergensis, Dav.,is not easy to define. It possesses very definite dental plates which are more vertical than those in MMacandrevia. he cardinalia, however, is not unlike that of Dallina septigera and floridana, i.e. typically Magellaniform.
With regard to Zerebratula frontalis, Midd., this possesses somewhat obscure dental plates much as in Zerebratalia. Its loop development and cardinalia suggest relationship with the Terebrataliform stage of Macandrevia cranium as figured by Beecher.’
Regarding the Cincta-like forms referred to Laqueus, the following notes, based on four of the species, may be of some interest :—
These species fall into two groups according to the character of the cardinalia. Lagueus pictus (Chem.) and LZ. rubellus (Sow.) possess obscure dental plates curving back to the apex of the valve. The hinge-plates in both are almost similar, consisting of two divergent buttresses rising from the floor of the valve and forming the dental sockets and crural bases. In Z. pictus these buttresses are divided clear to the apex, where a small bilobed cardinal process is present. In ZL. rubellus there is no cardinal process, the divaricator muscles being attached directly to the apical parts of the buttresses. Each species possesses a slight mesial septum which in old specimens is superimposed on a broad and massive base with deep muscle imprints on each side.
L. californicus (Koch) and B. blanfordi (Dunker) have better defined dental plates, which are almost vertical in the latter. The dorsal valves of both possess Magellaniform hinge-plates (as in Mf. flavescens); there is no cardinal process. L. blanfordi is the nearest to Cineta in outward appearance, as the interior margin is strongly indented. None of my specimens of ZL. californicus show the ventral plication as given by Davidson,? but only a tendency towards a truncated front. Possibly Davidson’s figure is incorrectly drawn.
The relationship of this Cincta-like group to the remainder of the Dallinine is difficult to decide. The peculiar double attachment of the loop suggests a complete divergence from the general line of Macandrevian development. <ingena (type, K. lima, Defr.), a species also possessing dental plates, seems to be a possible Cretaceous representative of the Laqueus structure.
As to the Magellanine having representativ es in northern oceans, this sub-family has a northern representative in Mihlfeldtia truncata (L.), an abundant species in the Mediterranean, and off the north of Spain, coast of France, etc.
Both the Anomia truncata, Linné, and the Anomia sanguinea, Chem.,
1 ** Revision,’’ ete., pl. i, fig. G1. 2 Op. cit., pl. xviii, fig. 6b.
24 J. W. Jackson—Brachiopod Morphology.
are given by Beecher’ as belonging to the same genus, viz. Mihlfeldtia, but this is incorrect, as dental plates are entirely wanting in the former and are well- developed i in the latter. é
A. truncata was made the type of Megerlia by King in 1850,’ but this name being preoccupied by a genus of Diptera in 1830, Bayle, in 1880,° established the genus Mauhlfeldtia for its reception.
Dall, in 1870,* placed sanguinea in the genus /smenia, King, but as this genus was founded by King on Terebratula pectuneulordes, Schl., > Dall, in 1895,° proposed Frenulina for the A. sanguinea, Chem.
Points of difference in the early stages of loop development, together with the presence of dental plates in one and their absence in another, seem good ground for the separation of these two, forms into different sub-families, Mihlfeldtia truncata being placed in the Magellanine and Frenulina sanguinea remaining in the Dallinine. The adoption of this course would necessitate the changing of the term Mihlfeldtiform stage in the Dallinine to Frenuliniform stage.
One remarkable point of difference in the development of the loop in I. truncata is clearly seen in the figure given by Fischer & Oehlert* of an early stage of this species. Here the loop is strikingly like the early stage of Tvrebratella dorsata, figured by Beecher.* There appears to be no stage like this in the Dallinine, where the descending branches of the loop appear early and are connected, thus forming a complete primary loop, whereas a feature of the Magellanine is the development of a secondary loop in the middle of the valve on the top of the septum, before the appearance of the primary lamelle. Deslongchamps’ figure ® of a young example of H. truncata, 2mm. in length, also shows a condition of loop somewhat similar to that of an adult Uegerlina lamarckiana (another member of the Magellaninz) figured by Beecher.” Some difference, however, is presented by the former having the ascending branches united to form a ring, whereas in 1. lamarckiana the ring is incomplete.”
The loop of Frenulina sanguinea, on the other hand, passes through early stages exactly like those of Macandrevia cranium.
RHYNCHONELLIDS.
In describing the manner in which the delthyrium of Hemithyris becomes partially closed, Thomson ” calls attention to a curious plate on the inner side of the apex of the pedicle valve. This plate, a kind of continuation of the deltidial plates, is free in front and separated from the shell by a narrow cavity. This feature, which I have termed the ‘‘pedicle collar’? in my forthcoming report on the
1 “* Revision,’’ etc., pp. 383-4.
* Mon. Perm. Foss. England (Pal. Soc.). Journ. de Conchyl., xxviii, p. 240, 1880. Amer. Journ. Coneh., vi, p. 129, 1870.
Not 7. pectunculus, Schl. ; see King, op. cit., p. 245. Op. cit., p. 724.
Op. cit., pl. vii, fig. 1lw.
Op. cit., pl. i, fig. Da.
Copied by Davidson, op. cit., p. 106, fig. 9. 10 Op. cit., pl. i, fig. Db.
11 See also Davidson, op. cit., pl. xxi, fig. 11. 12 Op. cit., p. 390.
ao ty Ona fF
©
J. W. Jackson—Brachiopod Morphology. 25
Brachiopods of the Terra Nova Expedition, is not by any means peculiar to the Rhynchonellids. It is present in Liothyrina, Terebratulina, and in all the short-looped forms I have been able to examine, some twenty-four recent species. It is also present in several fossil forms, including the large Crag fossil Zerebratula grandis, T. bisinuata from the London Clay, and Cyclothyris latissima from the Lower Greensand of Farringdon. In Terebratulina cancellata, Koch, the pedicle collar is strongly developed, and forms a perfect tube extending forward for some little distance, whilst in Megathyris decollata, Chem., it is well-developed and is supported by a sharp mesial septum. It is a structure which grows larger as the shell increases in size, and is the ‘‘doublure sous-apicale’’.and ‘‘doublure sous-cardinale’’ of Fischer & Oehlert.?
Judging from my own collection the pedicle collar is never developed in the higher long-looped forms; it is entirely absent from the following genera: Jlagellania, Terebratella, Dallina, Macan- drewia, Terebratalia, Laqueus, and Frenulina (type sanguinea). In some of these, however, there is occasionally a thickening in the umbo around the foramen assimilating a pedicle collar, but it is fused to the shell and never free anteriorly.’
_In the lower genera referred to the family Terebratellide a curious feature is present: Jlihlfeldtia truncata and Megerlina lamarckiana both possess a pedicle collar, but Araussina rubra does not; it only has a thickened plate fused to the floor of the umbonal cavity.
Genus rHerA,’ Thomson.
With regard to the relation of Rhynchonella lucida, Gould, to Thomson’s new genus thea, I possess a specimen of this form and find that it possesses fairly strong dental plates. This fact, together with the hypothyrid character of the pedicle passage, excludes the species from Atheia. Like Hemithyris psittacea there is no true cardinal process in the dorsal valve, the divaricator muscles being attached to the posterior ends of the crural bases.
_ The absence or presence of a cardinal process in Rhynchonellids seems to be a matter upon which some difference of opinion exists. In H. psittacea I have failed to find any structure iba ees to a true cardinal process, but in two large adult specimens of ‘ Hemithyris’
nigricans in my collection from Chatham Islands there is a small but distinct transverse bilobed cardinal process extending outwards like a shelf from the apex of the valve; the mesial septum in these specimens is also much stronger than in H. psittacea. In the ventral valve the dental plates are recurved towards the apex and net vertical as in H. pszttacea.
Regarding dental plates, etc., a close study of the fossil fering of the nigricans group would no doubt reveal some interesting features. The Manchester Museum possesses three specimens belonging to this group from the Table Cape Beds at Wynyard, Tasmania. One of these specimens is apparently closely related to H. nigricans; the
1 Hxpéd. Scient., pp. 44, 108, ete.
2 In old adult shells of Hemithyris psittacea the pedicle collar sometimes becomes fused to the floor of the umbonal cavity of the ventral valve.
26 Professor Percy Kendall—Glacier Lake Channels.
surface of the valves is ornamented with about thirty ribs, which are rather more angular and squamose than in typical nzgricans ; a mesial septum is also visible through the shell of the dorsal valve. Without spoiling the specimen it would be impossible to study the internal characters.
The two other specimens, one broken, the other perfect, are quite distinct from that described. The valves are ornamented by about forty-six radiating coste, increasing by bifurcation. The cost are divided by moderately deep furrows and are surmounted by short tubular spines which are arranged concentrically, following the growth-lines. The dimensions of the perfect specimen are as follows: length 16°5mm., breadth 19 mm., depth 7°5mm. ‘The imperfect example represents a shell of approximately the same size, and is interesting as it exhibits the internal characters. The teeth of the ventral valve are supported by very distinct dental plates, which ditfer entirely from those of H. nigricans by being almost vertical and more like those of H. psettacea. The foramen is rather large and the pedicle collar somewhat weak, as are also the deltidial plates. The dorsal valve possesses a thin mesial septum extending to the apex, while the dental sockets and crural bases are more divergent than in H. nigricans and psittacea. No cardinal process is visible.
I am unable to identify the above species with accuracy owing to the absence of specimens for comparison, but it seems to be related to Rhynchonella squamosa, Hutton = calata (M‘Coy MS.), Woods = pyxidata (Watson MS.), Davidson.
Hemithyris imbricata, Buckman,’ from the Miocene-Oligocene beds of Cockburn Island, off Graham Land, Antarctica, is near to it in general appearance, but this species appears to possess no dental plates.
Another species possessing some resemblance to the one under discussion is Rhynchonella (?) tubulifera, Tate,* from the Oligocene of Muddy Creek, Victoria.
VIl.—Guactrr Lake CuHannets. By Percy Fry KENDALL. N 1902 I published a paper,? the outcome of several years’ observation, on certain phenomena associated with the glacial
deposits of the Cleveland area, which I attributed to the former presence of a series of temporary lakes and lakelets upheld in the recesses of the hills by the margin of a great ice-sheet occupying the greater part of the North Sea. This interpretation met with so wide an acceptance, even by those geologists familiar with the district who had previously attributed the glacial deposits to a marine origin, that during the succeeding thirteen years I have steadfastly refrained from replying to criticism, hoping by this abstention to keep the issues unclouded by a controversy that might at any stage develop an acerbity not always lacking in earlier discussions.
1“ Antarctic Fossil Brachiopoda, etc.’’: Wiss. Ergebn. Schwed. S.P. Exped., 1901-3, Bd. iii, No. 7, 1910.
2 Trans. Roy. Soc. S. Australia, xxiii, p. 257, 1899.
3 Q.J.G.S., vol. lviii, pp. 471-571.
Professor Percy Kendall—Glacier Lake Channels, 27
Professor Bonney has favoured me with a copy of a pamphlet! in which he subjects my views to a criticism based upon a careful examination of parts of the area. Not content with mere destructive criticism, he elaborates in some detail an alternative explanation. The whole paper is so moderate, and the author’s appreciation of my work so generous, that I must break through my self-imposed rule of silence, and this I do the more willingly as no other critic has ventured to suggest any other hypothesis.
I may briefly recite the phenomena to be explained. A great series of sharply-cut ravines, in some cases veritable gorges, traverses the country, either within the area occupied by glacial deposits or just beyond its margin. ‘Their transverse section closely resembles that of a railway cutting, with which Professor Bonney aptly compares them ; there is the steep ‘batter’, the flat floor, and, let it be particularly noted, a comparable sharpness in the angles at the top and bottom of the slope. Sinuous channels have a steep batter on the outsides of bends, and gentler slope on the inside curve, just as we find in the ease of the banks of a river, though not commonly of a river valley. I draw two inferences from these features: (1) that the channels were excavated rapidly by a volume of water sufficient to occupy the whole floor, (2) that their formation was so recent that denudation has done little to modify the original contours.
As regards situation, they are found cutting through watersheds, even the main water- parting of the whole district (e.g. Newtondale), and sometimes trenching. boldly projecting spurs. Often a succession of spurs are cut along a line, as though an originally continuous ¢ehannel had been segmented up by the development of cross-contour valleys of normal type. A feature which opposes this interpretation is that, instead of the fall-line constituting a continuous gradient from end to end of the series, the outfall level of one segment generally coincides with the intake-level of the next, even though a distance of a mile or two may intervene. This arrangement is explicable on the supposition that the intervening space was occupied ‘by the standing waters of a lake, but is difficult to reconcile with an original continuity of the channels. Similar relations have been observed in many parts of Scotland and of the North of England.
Another significant arrangement is that which I have called a ‘* Parallel Sequence ’’, that is, a series of parallel channels cutting at successively lower levels a single spur. They fall in the same direction, and there is a method indicated by their relative heights ; each channel, as a rule, commences to break the ridge-line of the spur at almost the exact level of the intake of the next higher channel, as though—this is my explanation—the channels drained a lake held up by an ice-barrier, and when the ice withdrew so as to uncover a slope below the intake level, the drainage was diverted and the formation of a new channel begun. In some cases six, eight, or even more channels traverse the same spur in a distance of a mile or two. No comparable case of river-capture is known to me, and I am unable to imagine conditions which would produce such an effect. The
1 On certain Channels attributed to overflow streams from ice-dammed lakes.
28 Professor Percy Kendall—Glacier Lake Channels.
systematic disposition of the channels is still more comprehensively exhibited when a larger area is embraced in the review. The Cleveland area illustrates this fact with admirable clearness, for which reason I entitled my description ‘‘ A System of Glacier-lakes in the Cleveland Hills”’.
On the northern face of the hills I found evidence of a series of lakes draining, some to the westward of a dividing-line by a set of lake-to-lake channels into a lake in upper Eskdale; another set draining eastward to a main overflow by which they discharged into the samelake. The lake in Eskdale was, I supposed, upheld by a lobe of ice that stood across the Esk, leaving a mass of boulder-clay near Lealholm as a species of moraine. I may remark in passing that, as Professor Bonney no doubt observed when he visited the place, this supposed moraine divides the Esk Valley into two parts of surprisingly different topography, the upper part characterized by enormous terraces of ancient (lake-)alluvium, and the absence of any boulder- clay hills or other characteristic glacial features, as well as of gorges. along the course of the river; while, below this obstruction, the tumultuous heaps of boulder-clay and other Drift deposits, and the succession of gorges through which the river passes form a contrast as complete as could be desired to the tamer river-scenery of the higher reaches.
The ice-lobe similarly obstructed the tributary valleys on the south side of Eskdale, and not only are there masses of boulder-clay obstructing their lower ends and producing topographic contrasts. comparable with those of the main valley, but the spurs are trenched by channels by which the lake-waters evaded the obstacles. To. complete the series these channels conducted to a lakelet near Goathland, and thence across the main Cleveland watershed by the giant trench of Newtondale into the Vale of Pickering.
Space does not permit me to discuss in full detail the whole system, and it would be hardly fair to my courteous critic to evade the issues specifically raised by him. I will therefore confine my attention to one district of which his knowledge is almost as recent and probably as. full as my own, viz. the country between Fen Bogs, near Goathland, and the Esk Valley at Egton Bridge. The interested reader will find it fully pourtrayed in the map with 25 ft. contours in my paper already referred to (pl. xxii), or, better still, in the Proc. Yorks Geol. Soc., 1903, pl. vi.
The general build of the country is fairly simple—the axis of the main Cleveland anticline runs W.-KE., about through Julian Park. The River Esk flows along an inflection of the northern slope of this fold. The Murk Esk, a tributary of the Esk, rises by two heads, Eller Beck and Wheeldale Gill, from the south side of the anticline, and these streams, after flowing for distances of one and two miles. respectively towards the south, recoil from an opposing escarpment and swing round across the anticline—a very clear case of ‘stream trespass’, as Fox Strangways showed.
The ‘ certain channels’ in this area are—(1) Two parallel trenches on Murk Mire Moor, beginning as open notches on the bold scarp over- looking the Esk Valley within a mile or a mile and a half of the
Professor Percy Kendull—Glacier Lake Channels. 29
river, and respectively 450 and 600 feet above its level. ‘hey cut across a prominent spur and then coast along it fortwo or three miles, and finish almost as inconsequently as they began. (2) A headland, Two Howes Rigg, separating Wheeldale Gill from Eller Beck, is trenched by achannel about a mile long that carries on the chain to within about a mile of the beginning of Newtondale, a tremendous ravine that attains a depth of 250 feet where it passes through the escarp- ment formed by the Kellaways Rock.
Professor Bonney regards these ‘ channels’ as relics of a very ancient river system that has been encroached upon by a more energetic system, namely, that of the Murk Esk. In my first attempts to elucidate the river development of the Cleveland area I attributed the principal role to river-capture, and presented it for discussion at a meeting of the Yorkshire Geological Society, but later, when I descended to details, I found insuperable difficulties, and I think Professor Bonney will recognize their importance. Firstly, the lower channel on Murk Mire Moor—as I have mentioned, begins with a perfect railway cutting section within one mile of the River Esk and 450 feet above it. The floor falls, not towards the river, but away from it, with a fairly steady gradient except for accumula- tions of peat and a small amount of running down of the sides. The upper channel falls in the same direction, and the channel on Two Howes Rigg continues the course, but from west to east. After ashort interval the great gorge of Newtondale, falling south, com- pletes this series. I ask, is it likely that two rivers could have flowed backward across the Cleveland: anticline and away from the Esk, the main drainage line of the district ?
Their sections, as [ have pointed out, indicate that they carried a large volume of water. Whence was it flowing? Several alterna- tives might be suggested—(1) That the channel had been deprived of its headwaters by the widening of the Esk Valley. This, unless the course of the Esk has been materially altered, would increase the drainage by one mile, and then only on the assumption of a vertical side to the Esk Valley. (2) That the Ksk itself flowed this way and cut the Newtondale channel as well as those along the Moor-edge. Such a readjustment of drainage is not only opposed to the whole build of the country, but it seems negatived by the behaviour of Wheeldale Beck and Eller Beck, which shows that the ‘trespass’ was all in the opposite direction (i.e. encroach- ment across the anticline by the Esk by virtue of the ‘law of steepest slope’). (8) That there was no Esk Valley at the time when these channels were operative and that the drainage of the North Cleve- land hills, ignoring syncline and anticline alike, came over into this system. Ido not think such a hypothesis needs any refutation, for Professor Bonney expresses the opinion that the original watershed was ‘‘rather more than a quarter of a mile north of Goathland Station”. This is almost exactly on the axis of the anticline. A watershed in such a position would, however, attach the Murk Mire Moor channels to the Esk drainage, although they slope directly away from it.
(To be continued.)
30 Notices of Memoirs—A. Coa—Ordovician, Cader Idris.
NOTICHS OF MEMOTRS.
I.—Tue Orpovictan Srquence In THE Caper Jpris Disrricr (MerionetH).1 By Arrnur Husperr Cox, M.Sc., Ph.D., F.G.S., and ALFRED Kinestey WELLs.
EFERENCE was made to the work of previous observers, including Sedgwick, Ramsay, Cole and Jennings, Geikie, and
Lake and Reynolds.
The Cader Idris range is formed by a great escarpment of Ordovician igneous rocks, facing northwards across Barmouth Estuary towards the Harlech dome.. The igneous rocks were for long regarded as being all of Arenig age.
Re-examination of the area has shown the presence of four distinct volcanic series among the Ordovician rocks, and the following descending sequence has been established—
f 10. Talyllyn Mud- Grey blue-banded mudstones with
Glenkiln-Hartfell . stones Amplexograptus arctus in the ( lowest beds . - . 800 ft. 9. Upper Acid or ‘Andesitic’ and rhyolitic ashes Craig-y-Llam and lavas . - 900-1,000 ft. Series 8. Llyn Cau Mud- stones 500 ft. 7. Upper Basic or Pillow lavas (spilites) with tuff and Pen-y-Gader chert bands ; . 3800 ft. Series Glenkiln with Upper } 6. Llyn-y-Gader Blue-grey mudstones with thin Lilanvirn Mudstones adinole -like bands and with and Ashes massive ashes above and below 450 ft. 5. DarkMudstones Frequently containing pisolitic ivon-ore . ‘ oats 4. Lower Basic or Pillowy spilitic lavas with inter- Llyn Gafr calated ashy and shaly bands, Series massive banded andagglomeratic ashes at the base . 1,500 ft. ° 3. Didymograptus Dark slates with well-marked ash Lower Llanvirn | bifidus Beds bands in the lower portion 500 ft.
2. Lower Acid or Rhyolitic ashes with some slates MynyddGader above, rhyolitic lavas below
Arenig . : : Series 300 ft. 1. Basement Beds Striped arenaceous flags and grits 100 ft. Unconformity Upper Cambrian . Tremadoc Beds
Both acid and basic rocks occur as sills at numerous horizons. The basic rocks are diabases of various types, all with the felspars considerably albitized and usually with primary quartz. The acid rocks are soda-granophyres. The granophyre intrusions cut and are later than the basic intrusions, and locally hybrid rocks appear to have been formed along the junctions. No basic intrusions have been found above the Upper Basic Volcanic Series, and no acid intrusions above the Upper Acid Series, and it is noteworthy that the
1 Read before the British Association, Section C, Manchester, 1915.
Notices of Memows—Prof. Wallace—Brines of Manitoba. 31
granophyres appear to be closely related to the extrusive rhyolites among which they are intruded. This fixes an upper limit to the age of the diabases in this district.
The various beds strike more or less east to west, and dip steadily southwards at about 40° until the Talyllyn Mudstones are reached, when folding and rolling of the beds immediately begin. Two N.E.-S.W. shatter faults—the Dolgelley and Talyllyn faults—cause a certain amount of repetition, and give rise to the Dolgelley-Llyn Gwernon and to the Talyllyn Valleys, the former to the north and the latter to the south of the escarpment. A strike-fault between Mynydd Gader and Cader Idris cuts out the whole of the Bifidus Beds, bringing the Lower Acid and the Lower Basic Volcanic Series against one another. The intrusive rocks frequently cause local variations in the dip and strike.
All the softer strata are strongly cleaved, so that fossils are difficult to obtain. The slates within the Lower Acid Series have yielded a few extensiform graptolites, while from the Bifidus Beds the characteristic fossils were obtained at numerous localities. The D. murchisont zone has not been recognized by the authors, its place presumably being occupied by a part of the Lower Basic Series. The dark mudstones among which the pisolitic iron-ore is developed have yielded rather obscure graptolites, which, however, indicate a fairly high horizon in the Llandeilo Series. The presence of Amplexograptus arctus and Glyptograptus teretiusculus var. euglyphus in the lowest beds of the Talyllyn Mudstones indicates a high horizon in the Glenkiln, or, in other words, a low horizon in the Caradocian, and suggests that the immediately underlying Upper Acid Series is at
approximately the same horizon as the Snowdonian volcanic rocks of - Conway. This youngest of the four volcanic series on Cader Idris is therefore considerably higher in the Ordovician than has been previously supposed. The position of the boundary between Cara- -docian and Llandeilian has not yet been established, owing to the unfossiliferous character of the blue-grey mudstones of Llyn-y-Gader and Llyn-Cau.
One of the authors (A. H. Cox) is indebted to the Government Grant Committee of the Royal Society for a grant which has partially defrayed the expenses involved in the investigation. The area is being mapped on the 6 inch scale.
II].—Tne Corrostve Acrion oF CERTAIN Brines In Maniroza.’ By Professor R. C. Wattacr, M.A., Ph.D., B.Sc.
RINE springs issue from Middle and Upper Devonian limestones. and dolomites at the foot of the Manitoba escarpment. At least eighty brine areas are known, with a total flow—during the dry season—of approximately 500 gallons per minute. The water circulates in the Dakota Sandstone, the basal member of the Cretaceous series, and extends laterally into the Devonian calciferous formation, from which it leaches sodium chloride, disseminated through certain dolomite horizons. The composition of the brines,
1 Read before the British Association, Section C, Manchester, 1915.
32 Reviews—Professor A. Keith—Antiquity of Man.
expressed in percentages of total solids, is very similar to that of sea-water. It is a somewhat purer solution of sodium chloride, and also a more concentrated solution, than sea-water, the percentage salinity being 5-7 (sea-water 3:5).
The salt-flats where the springs reach the surface are devoid of vegetation and studded with ice-carried boulders. These are representative of the pre-Cambrian igneous series of North-Central Canada—granites, gneisses, and epidiorites. They have suffered intense chemical disintegration, large boulders having been reduced to half their original size. Different minerals have been affected to different extents, but not even quartz or garnet has escaped corrosion. Ferromagnesians have been most intensely affected; and gneissose structures, hardly noticeable on unweathered surfaces, stand clearly revealed. The striking difference between the action of these brines and that of sea-water calls for explanation.
Thin crusts of salt gather, during the summer months, on the flats and around the boulders. The salt is somewhat deliquescent ; and thin films of brine are drawn, by surface tension, over the surface of the boulders. Water in contact with the atmosphere is a powerful disintegrant. Alkalies are removed as chlorides or carbonates, and silica and alumina are precipitated as gels, separately or in com- bination. The gels exercise selective adsorption on the salts of the brine, alkali being taken up and the brine being left richer in the acid radicals. The brine is thereby rendered a more active dis- integrating agent, and the process goes on continuously. ‘The function of the dissolved salts is considered to be twofold: (1) they provide a thin film of liquid in contact with atmospheric oxygen ; (2) owing to partial adsorption by colloids, they provide an acid residual solution, which is a powerful corrosive agent.
The evidences of the corrosive action of sea-water on beach boulders are no doubt obscured by mechanical attrition due to wave action.. Such corrosion cannot, however, be compared in intensity with that of the brines. Boulders between high- and low-water mark are alternately submerged and dry to the base—a state of affairs inimical to the persistence of thin films of liquid on the surface of the boulders. The initial conditions are consequently wanting ; and the relative immunity of beach boulders from chemical corrosion is due, not to any inability of sea-water to act as a corrosive, but to the absence of favourable conditions for the activity of the solution.
REV LHwsS-
I.—Tue Antiquiry or Man. By Artuor Kerra, M.D., F.R.S. pp. 519, with 189 text-figures. London: Williams & Norgate, 1915. Brace 10s. 6d. net.
fP\HE subject of the antiquity of man seems naturally to fall to the
geologist, with such aid as he can obtain from the human anatomist and archeologist. The value of the evidence which has to be considered can only be estimated by one who has a practical acquaintance with geological problems in the field. From Lyell onwards, therefore, all the most important works dealing with the
Reviews—Professor A. Keith—Antiquity of Man. 33
question have been written by geologists; and he is indeed a bold man who would form independent judgments on the materials taken at second hand. Now, however, a distinguished human anatomist has entered the field, discussing the antiquity of man from his own point of view and trusting to such quotations from geological literature as suit his purpose. We therefore turn with great interest to Professor Arthur Keith’s handsome volume which has just been received.
Professor Keith writes in an attractive style, and though at times his matter is somewhat technical his explanatory figures are so numerous and clear, placed as they are in frames of standard magni- tude, that even the non-anatomical reader will find no difficulty in appreciating his points. His story, indeed, is that of an eager student ever searching for the meaning of things, and it gives an excellent idea of the aims and methods of modern physical anthropology. Our only regret is that lack of a geologist’s caution permits him to make dogmatic statements about the age of the various remains in terms of years, which will doubtless give gratifying satisfaction to an unwary public, but will also deceive them in an unfortunate manner.
Professor Keith begins with Neolithic man, and shows that he differs in no respects from the men of Europe at the present day. His description of the discovery of his remains in the megalithic monument at Coldrum, Kent, is a good example of his picturesque writing. We hardly appreciate the comparison of this monument, however, with the Sardinian ‘giant’s tomb’, when the relative proportions and positions of the stones have to be so much altered to make it plausible (cf. figs. 3 and 9).
Proceeding to Paleolithic man, Professor Keith shows, from the well-authenticated cases of Paviland, Engis, and Cro-Magnon, that at least the later races were also similar to those of modern civilized man. He then soon begins to illustrate the disadvantage of his _ position by accepting as valid evidence a series of human remains, ot which scarcely any—perhaps none—can be regarded with certainty as belonging to the age of the stratum in which they occurred. He even continues to believe that the Galley Hill man dates back to the Chellean period, and thinks that the Ipswich man may be earlier. Thus he assigns a much greater antiquity to modern man than a cautious geologist or paleontologist would be disposed todo. In fact, he introduces unnecessarily an anomaly into the series of undoubted fossil human remains which accord with paleontological theory and expectation.
Of these undoubted fossil remains Professor Keith gives an excellent account, enlivened by his own observations, and treats in succession of Neanderthal man, Heidelberg man, Pithecanthropus, and Koanthropus. The discussion of the latter genus, or Piltdown man, is especially interesting, and occupies no less than 200 pages. The precise result is a little obscure, but Professor Keith now admits that the chimpanzee- like lower jaw was correctly restored by the paleontologist, and he has considerably reduced his original estimate of the size of the brain-case, which he thinks cannot have exceeded 1,400 c.c. We can only express the hope that Mr. Charles Dawson will continue his
DECADE VI.—VOL. III.—NO. I. 3
34 Reviews—Prehistoric Archeology.
researches in the Piltdown gravel, and discover more nearly complete specimens which may solve some of the problems that still remain inexplicable.
IJ.—Preuisroric Arco Z0LoGyY.!
ial the first paper in the list Professor McKenny Hughes deals with
flint, its origin and destruction, and the extent to which chipped flints are reliable evidence of the presence of man. The paper is founded mainly on the series of specimens brought together in the Sedgwick Museum at Cambridge. The following paragraph deserves serious consideration nowadays: ‘‘ Let us now take a few groups of naturally shaped flints. First there are those which are called ‘Figure Forms’. M. Boucher de Perthes was the first to call serious attention to them. He was the man who in 1857 announced the discovery of palzeolithic implements in the valley of the Somme; and it is often said in reply to those who criticise adversely the evidence upon which a more remote antiquity is now claimed for man than had been previously supposed, that, the same thing was done in the case of Boucher de Perthes’ discoveries. But the rejoinder is obvious. Had Boucher de Perthes not supported a correct theory by bad evidence the acceptance of his views would not have been so long retarded. We cannot in science give a bill of indemnity for false reasoning, though it was in support of a suggestion which after- wards turned out to be true.”
Dr. Holst in the second paper gives a short and very clear account of the prehistoric flint-mines near Malmo in Southern Sweden. These pits are sunk in gigantic erratic blocks of chalk, the largest being about 3000 x 1500 x 10-20 feet.
Though necessarily much smaller, on account of the shattered state of the anal these shafts are comparable to those of Grimes Graves, which they resemble in having been hewn out with stag’s horn picks. The implements and scrap from the sites, however, do not closely resemble those from the English locality, and seem to show that these mines were worked from the later part of the Neolithic to the Early Iron age.
The third work under review is an excellent piece of archeological survey, detailing the camps and graveyards, the rock-shelters and trails of the Red Indians in certain parts of New Jersey. It consists of a mass of facts well illustrated by maps, plans of rock-shelters, and photographs of pottery, of great local interest, but impossible of review. It is, however, an illustration of the interest which citizens
1 Professor T. McKenny Hughes, ‘‘ Flints’’?: Cambridge Ant. Soc. Coll., vol. xvili. .
Dr. N. O. Holst, ‘‘ The Swedish Flint Mines’’: Report on the Excavations at Grimes Graves, 1914.
M. Schrabisch, ‘‘ Indian Habitations in Sussex County, New Jersey ’’; and L. Spier, ‘‘Indian Remains near Plainfield, Union Co., and along the Delaware Valley ’’: Geol. Surv. New Jersey, Bull. 13, 1915.
N. H. Winchell, ‘‘ The Weathering of Aboriginal Stone Artifacts. No. 1. A consideration of the Palsoliths of Kansas’’: Collections of the Minnesota Historical Society, vol. xvi, pt. i.
Reviews—O. P. Hay—Mammals of Iowa. 35
of the United States feel in the history of their country, and the thoroughness with which they are recording the fast vanishing remains of the splendid savages whose place they have taken.
The last archeological work which it falls to me to review claims to deal with the Paleoliths of Kansas. The author divides up a series of implements into four groups, two said to be of Paleolithic age, the others later and early Neolithic. He correlates them with the many glaciations of North America. All these specimens seem to be surface finds. None were found with extinct animals or in relation to glacial deposits. The whole scheme rests entirely on depth of patination and on certain implements which are said to be rechipped. Some of the implements photographed do resemble genuine paleoliths in shape, but others are as obviously allied to modern Indian work.
The whole book is a somewhat pathetic example of misapplied energy. There is not the slightest evidence that any one of the American implements described was made during the Ice Age or before it. So far as I know, only one implement has been found in America that has any claim at all to be considered a palzo- lith, the arrowhead found by Professor Williston in association with an extinct bison; and this is of a relatively modern Indian type.
II1.—Tue Puristocent Mammats or Iowa. By O. P. Hay.’
oe paper consists of 499 pages of text and 75 plates, mostly from i photographs. It begins with avery valuable account of the main facts of the glacial geology of Lowa, describing the distribution of the tills laid down during five glacial stages and of the deposits associated with the interglacial intervals. This section is provided with an elaborate bibliography.
The second part of the paper gives in as untechnical a way as possible, descriptions of the animals found in the Pleistocene of this State, together with some that will no doubt be found in the future. ‘These descriptions are founded on Iowan specimens, but when these are incomplete others are figured and their measurements given. The whole forms a very valuable work of reference, full of clearly arranged facts, but does not seem to contain any general conclusions as to the relations of the many animals discussed to the divisions of Pleistocene time ; in fact, the existing collections seem to be still too small to yield much in the way of wide generalizations.
TV¥.—Txe Coat-mMEasuRE AMPHIBIA AND THE Crossopreryera. By R. L. Mooprs.?
N this short paper Dr. Moodie gives a phyletic tree of the vertebrates, of interest as representing the views of a student with great knowledge of the smaller Coal-measure amphibia, still unfortunately so very incompletely known. He then gives a short summary of the geological history of the amphibia, which is slightly
1 Towa Geological Survey, vol. xxiii, 1914. 2 The American Naturalist, vol. xlix, p. 637.
36 _Revrews—The Trilobite Harpes.
incomplete in not Sea the amphibia from the Mississippian of Scotland and the frog from the lithographic slate of Portugal.
A comparative table shows that in many features the Crpeas: pterygian fish and the amphibia approach one another. Finally, the high degree of specialization and complete adaptation to nearly all conditions of vertebrate existence of the Coal-measure amphibia is insisted upon.
V.—New Yorx Strate Museum. Patzxozorc Fisuus, Erc.
ESTORATIONS of Bothriolepis and Cephalaspis as restored by Patten and modelled by Marchand are figured as among the new items on exhibition in New York. The State mining exhibit at the Panama-—Pacific Exposition is described, and a report is given on the preservation of natural monuments. These latter, now added to the former trusts, are the Lester Park (or the “‘ Oryptozoon Ledge’’), Stark’s Knob, a dome-shaped volcanic knoll, the Clark reservation (a glacial park), Logan Park (where W. E. Logan began his official work) with its vertical ledge of Ordovician or Cambrian limestone-conglomerate, and the Hugh Miller Cliffs, Scaumenac Bay, celebrated for their Old Red fishes. All these places are briefly described in the Museum Bulletin 177 of the New York State Museum, 1915. This Bulletin also contains, we believe for the first time, an excellent attempt at depicting a ecological section by colour photography. ‘There is a short paper by Hudson on Porocrinus; others by Clarke on American Devonian, the Oriskany, and the Rifted-Relict-Mountain ; and by Miller on Trenton Contortions and the Rift on Chimney Mountain. Among accessions we note the Silas Young minerals.
ViI.—Srrucrurt or tHE Tritosire A ARPzS.
N preparation for a monograph on the trilobite Harpes, Dr. Rudolf Richter has studied the structure by means of thin sections, and
_ has presented an outline of his main results in Zoologischer Anzerger , (vol. xlv, pp. 146-52, Dec. 1914). He finds that’ the pits on the brim (French ‘limbe’, mistranslated as ‘limb’ by several English writers) are not blind, as stated in text-books, but pierce right through. Precisely the same structure extends over a considerable tract “of the swollen part of the head-shield. All this perforate extension is composed of two distinct layers (outer and inner) of chitinous integument. From the inner boundary of the inner layer a thin ventral membrane extends below the true head cavity. ‘he marginal suture (on the outer edge of the brim) has been regarded as the ocular suture, and the under fold of integument as the free cheeks; and on this view depended Beecher’s conception of the Hypoparia. A corollary of that view was that the eyes on the upper surface could not be homologous with the true eyes of other trilobites. Richter, however, shows that the microscopic structure is quite opposed to that forced hypothesis. The eyes are true eyes, and though the ocular suture is obscured the free cheeks occupy the nano position. The marginal suture is, in his opinion, a special
Reviews—Edriouasteroidea. oF
development to permit the separation of the under layers of integu- ment in course of moulting, and traces of this division between the two layers, though sought in vain by some previous writers, have been found by him on the sides of the perforations. Consequently Harpes, Trinucleus, Dionide, and the rest, though highly specialized, are not essentially different from other trilobites, a view which accords with that expressed by Professor Swinnerton in the Groroercat Macazine for November, 1915. Dr. Richter also elucidates the peculiar method of rolling up the carapace, and believes that the backwardly directed horns of the head-shield served, not as ‘mud-shoes’, but as balancers when the animal swam; a similar balancer- function has been ascribed to the horns of Ceratocystis, Cothurnocystis, and Dendrocystis (see Grot. Mac., Sept. 19138, plate xii).
VII.—Srvupms rn EprroasreromEa, I-IX. By F.A. Barner, M.A., D.Se., F.R.S., etc. 8vo; pp. 136, with 13 plates. Published by the author at ‘‘ Fabo”’, Marryat Road, Wimbledon, London, 8. W. 1915. Price 10s. 6d.
Jae highly, important work, completed in the past year, was begun as a series of articles in the Grotocican MaeazinE in 1898 and continued, with intervals, until 1915, extending over seventeen years. In the reprinted form there will be found some valuable additions, and the very numerous illustrations in the text, as well as the thirteen beautiful plates, are all reproduced with care. To any student desirous to become acquainted with the morphology and classification of the Echinoderma the present work must form an essential part of his library; and as the original ‘‘Studies’’ are scattered through the volumes of the GrotocicaL Magazine during so many years, we must all feel extremely grateful for the ‘‘ Author’s Edition ’’, as Dr. Bather calls this volume.
We heartily congratulate the author upon his completed work, and wish him many more years in which to continue his difficult but
‘delightful studies of other sections of the Echinoderma.
Vill.—Caratogure or Types anp Ficurep SprcIMENS oF BritIsH CRETACEOUS LAMELLIBRANCHIATA PRESERVED IN THE MUSEUM OF Pracrican Gxzotocy, Lonpon. Summary of Progress of the Geological Survey for 1914, Appendix II, pp. 66-79, 1915.
R. H. A. ALLEN, F.G.S., one of the Paleontologists of the Geological Survey, is the compiler of this very excellent and nseful work. It forms the eighth of a series of similar lists which have been issued under the same auspices, the previous subjects treated being Eocene and Oligocene (1900); Pliocene, Pleistocene, and Devonian (1901); Phyllocarida and Paleozoic Echinodermata (1902); Rhetic, Lias, and Inferior Oolite Gasteropoda (1908) ; Great Oolite, Cornbrash, and Corallian Gasteropoda (1904); Rheetic and Lias Lamellibranchiata (1905); Lower, Middle, and Upper Oolite Lamellibranchiata (1906). These catalogues are all modelled on the same plan, the genus and species of each entry standing out clearly in a bold black type, followed by the author’s name, beneath
38 Reviews—Prof. J. Barrell—Isostasy.
being the reference in literature where the description and figures are to be found, and afterwards are given the geological horizon, locality, and registration number. A valuable addition, we think, might have been introduced in connexion with the geological information offered, that of Continental equivalents, as for instance, when quoting the horizon of the Atherfield Beds as ‘ Lower Green- sand’ the term ‘ Barremian’ might have been given in brackets. A modification of this kind would have been most welcome to the foreign student of geology in enabling him at once to understand the value of a purely English term and its exact significance in the Cretaceous Series. It is interesting to mention that this catalogue differs from all the former, as it includes a number of type or figured specimens that were originally in the Museum of the Geo- logical Society of London, these being indicated by the letters G.S.
EN.
IX.—Isosrasy, AND THE ASTHENOSPHERE.
Tur Srreneru or tHE Earrn’s Crust. By Josnpa Barrett. Journal of Geology, vol. xxii, pp. 28, 145, 209, 289, 441, 537, 655, and 729, 1914; vol. xxiii, pp. 27, 424, and 499, 1915.
N this remarkable series of papers, which is worthy of the most careful study, Professor Barrell discusses the problems arising from the existence, now well established, of isostasy. He shows from geodetic data and from geological evidence (e.g. the building up of extensive deltas) that ‘‘isostasy . . . is nearly perfect, is very imperfect, or even non-existent according to the size and relief of the area considered”. The close degree of isostatic equilibrium postulated by Hayford is not admitted, but since over large areas equilibrium is maintained in spite of denudation, deposition, and mountain- building, it follows that there must be some counter movement taking place within the earth. To explain the mechanism of isostatic compensation Barrell introduces the conception of an asthenosphere— a sphere of weakness—which, as he clearly shows, must be below the level of compensation, and of great thickness. The excess pressure of heavy columns of the lithosphere is transmitted to the asthenosphere, within which the lateral movements of restoration take place. In proof of the existence of some such zone of weakness the author indicates the impossibility of widespread flowage in the zone of compensation; he shows that below the level of compensation the earth is unable to withstand the stresses thrown upon it by the greater undulations of topographic relief; and finally he cites Schweydar’s conclusion, based on measurements of earth tides, that there seems to exist a yielding layer 600 kilometres in thickness below the 120 kilometres of the lithosphere.
It is suggested that recrystallization is the chief factor determining weakness, plasticity, and flowage. It should be remembered that effective plasticity, signifying a low elastic limit, is by no means incompatible with a high rigidity. The flowage of glaciers is an instructive case in point. Recrystallization will clearly be favoured by high temperature conditions. This leads to another line of
Reviews—Delta Deposits of the Nile. 39
argument supporting the existence of the asthenosphere, for the distribution of the radio-elements in the earth’s crust carries with it the deduction that fusion temperatures (under high pressures) can only be approached far below the level of compensation, probably 200 km., or more, below. In keeping with this view, Barrell holds on mechanical grounds that the source of igneous activity is well within the asthenosphere. Recrystallization, culminating in local fusion, is brought about by the gradual contact of the temperature curve with the fusion-solution curve, and ‘‘if this is the cause of the disappearance of strength, it should be as much as 300 km. deep and extend through some hundreds of kilometres”’. The author draws a short sketch of the initiation of magmas and their ascent into the crust. He supposes that they are of basaltic or andesitic composition, though in the opinion of the present writer the possibility of the rocks at such depths being wholly of ultra-basic composition is worthy of consideration, together with the mechanism of igneous intrusion implied by that view.
Professor Barrell’s papers constitute a valuable and imme contribution to terrestrial dynamics, only the fringe of which has been touched upon in this brief and therefore inadequate review.
ArtHur Homes.
X.—Detra Duposrrs or tHe Nite.
Tae Suzsor. or Carro. By E. C. Bowpen Surrg. Cairo Sci. Journ., Nos. 97 and 98, vol. viii, pp. 289-50, with 3 plates, 1914.
NE of the most interesting problems connected with the delta deposits of the Nile is their evidence on the supposed isostatic movements of the area; and Mr. Bowden Smith discusses the evidence of many bores under the Nile delta upon the supposed subsidence. He quotes Professor Watts to the effect that the old soils, one below another, prove conclusively the repeated subsidence of the delta, and he remarks that according to other authorities the ‘low-level deposits at least were laid down beneath the sea when it extended southward up the Nile Valley. Mr. Smith states that the delta is not composed of an endless succession of interlaced deposits of sand and clay; he concludes from the nature of the deep-level deposits and their irregular distribution there is reason to believe that they were formed by river-action working under conditions similar to those that prevail on the surface at the present day. The author remarks that the evidence on this question is not conclusive, and that some of the deep-level material may be marine, but he holds that repeated substances have taken place between long intervals of rest.
JWG:
XI.—Doetrer’s Hanpsoox or Mrneratoay.—We recently received the fourth part (Dresden and Leipzig: Theodor Steinkopff. Price 6.50 marks) of the third volume of the comprehensive Handbuch der Mineralchemie, edited by Professor C. Doelter, which was issued in July, 1914, just before the outbreak of War. It forms the penultimate part of the volume, and in its 160 pages deals with the
40 Reviews—Russian Meteorite.
concluding species among the phosphates and with the greater number - of arsenic compounds. A conspicuous feature of the work consists of the ample discussion of chemical methods which are introductory to the descriptions of the principal mineral groups; thus, in the present part we find an able article from the pen of Professor Dittrich on the analysis of the arsenates. The descriptions of the several species seems on the whole complete and up to date. We have under turquoise a good account of Schaller’s recent work on the specimens found in Virginia, which cleared up the mystery of the crystallization of that species and showed it to be isomorphous with chalcosiderite. Following the chapters on monazite and xenotime comes an interesting one on the commercial use of the so-called rare earths. We have noticed one important omission. In the section on tilasite, the calcium-magnesium arsenate, no reference is made to the memoir published by Prior & Smith in the Mineralogical Magazine in 1911 on the crystals found by Ferrar in the manganese-ore deposits of Central India. In consequence the crystallographical particulars of the mineral are reduced to the single—erroneous—sentence: ‘‘Kristallisiert vielleicht triklin”; the crystals, however, actually belong to the clinohedral class of the monoclinic system.
XIJ.—Russtaw Merrorrre.—In the Proceedings of the U.S. National Museum (vol. xlix, pp. 109-12, with plate xxxvii) Mr. George P. Merrill briefly describes the meteoric stone which fell at Indarch in Russia on April 7, or possibly April 9, 1891. It is a dark greenish-grey in colour, firm and compact in texture, and thickly studded with small, dark-green chondrules and nodular masses of metal and troilite, rarely more than 1 mm. in diameter. Graphite is very prevalent. Oldhamite, calcium sulphide, occurs sometimes interstitial and sometimes enclosed in enstatite; it is yellow-brown, sometimes greenish, in colour, and completely isotropic. The presence of carbonic acid in the analysis suggested breunnerite, but the actual occurrence could not be determined. The stone is a carbonaceous chondrite (Ke).
XIII.—Brisr Noricers.
1. QurnevenniAL Review oF tHE Minera Propuction oF Inpra. By Sir T. H. Hortanp and Dr. L. L. Fermor. Revised for the years 1909 to 1918 by Dr. H. H. Haypen and Dr. L. L. Frrmor. Records Geological Survey of India, vol. xlvi, 1915.
This valuable report contains a great deal of useful information regarding the occurrence of economic minerals in India. Listed according to their values the eight principal minerals are coal (£3,800,000 in 1913), gold, petroleum, manganese ore (about 40 per cent of the world’s production, and exceeded only by Russia), salt and saltpetre, mica (65 per cent of world’s production), and lead ores. During the period under review the tin and wolfram industries in Lower Burma have made considerable strides, while rubies and other precious stones have suffered some depression. The
Reports & Proceedings—Geological Society of Glasgow. 41
production of monazite from the seashore of Travancore marks the commencement of a new mineral industry.
2. On tHe Porosity or tHE Rocks or THE Karroo System In Sourn Arrica. By A. L. pu Torr. Trans. Roy. Soc. S. Africa, vol. iv, pt. 111, pp. 169-80, 1915.
The rocks of the Karroo system cover fully one-half of the Union of South Africa, and have sometimes been considered capable of furnishing important supplies of artesian water. The author has made a large number of measurements of porosity and specific gravity on fresh specimens from various horizons of the formations represented. His results show that the porosity of these rocks is low, and that, except where fissures and joints increase the capacity for water storage, strong supplies cannot be anticipated.
3. BrieHron’s Lost River.—Mr. K. A. Martin has contributed to the Transactions of the South-Eastern Union of Scientific Societies, 1915, a very complete account of the Wellesbourne, a stream which rose near the upper end of Patcham Street and entered the sea at the Pool, Pool Valley, Brighton. Its operations are now confined by a sewer, but in former days it seems to have been the cause of frequent flooding and other trouble to the town.
REPORTS AND PROCHHDINGS.
ee ——————. I.—GerotoctcaL Society or GLascow.
At a meeting of the above Society held on November 11, the office-bearers for the session were elected.
‘Mr. Alexander Scott, M.A., B.Sc., read a paper on “ Primary Analcite and Analcitation”. He discussed the occurrence and form of analcite in igneous rocks and reviewed the opinions of various authorities concerning it. British and American petrologists generally favour the opinion that the mineral is primary, while Continental investigators hold the view that it is secondary. The chief evidence in favour of the latter theory is the altered condition of associated minerals, but this can be shown to be due to reactions between the analcite and minerals previously formed; thus felspar is replaced by analeite, augite has a rim of soda-pyroxene, and olivine and magnetite are surrounded by biotite. These undoubtedly arise by the corrosion of the early minerals by a magmatic residuum rich in water and soda. The general conclusion is that analcite is primary in many rocks, particularly in the great Permo-Carboniferous suite of the West of Scotland described by Tyrrell.
Professor Gregory complimented the author on his paper, and said it was satisfactory to find that, while there was ground for the views of both the British and the Continental workers, the balance of truth lay with the British.
Mr. G. W. Tyrrell said that in addition to the evidence brought forward by Mr. Scott, the fact that analcite is such an important constituent (sometimes about 40 per cent) of many rocks points to its being a primary ingredient, as such rocks, minus their analcite,
42 Reports & Proceedings—Geological Society of London.
would be too spongy in structure to resist the pressures to which they had undoubtedly been subjected. He also compared its mode of occurrence with that of quartz in a granite, and thought that the two were quite analogous.
Mr. Peter Macnair, F.R.S.E., F.G.S., read a paper on ‘‘ The Horizons of the Type-specimens of Dithyrocaris tricornis and D. testudinea’”’. He detailed what was known as to the discovery of these interesting fossils, and pointed out that, while the facts connected with the East Kilbride occurrences were well ascertained, there was confusion with regard to the exact locality from which the Paisley specimens came and their horizon was not known. He stated that he had recently found specimens in an old dyke and an old house built of a peculiar limestone near Arklestone, Paisley, and showed that this material must have come from certain old quarries, now obliterated, and that these quarries must have been opened in the Blackbyre Limestone.
Mr. R. G. Carruthers, H.M. Geological Survey, said that he quite agreed that these specimens must have come from a peculiar bed lying at the top of the Blackbyre Limestone at Arklestone, and congratulated Mr. Macnair on having settled a question that had been for so long a source of discussion.
I1.—Grotoeicat Soctery or Lonpon.
1. November 17, 1915.—Dr. A. Smith Woodward, F.R.S., President, in the Chair.
Mr. John Parkinson gave an account (illustrated by specimens and lantern-slides) of the Structure of the Northern Frontier District and Jubaland Provinces of the East Africa Protectorate, made by him while conducting a water-supply survey for the Government of the Protectorate. A floor of gneisses and schists, among which the Turoka Series of metamorphosed sediments was found at several places, is overlain on the western side by lavas, including those arising from the volcanoes Kulal, Assi (‘Esie’ of the maps), Hurri, Marsabit, etc., and by probably older lava-fields, which together extend as far'as long. 39° E. On the south, it was found that the lavas north of Kenya reached the Guaso Nyiro, leaving ‘inselberge’ of the crystalline rocks in their midst, but that a high gneiss country extended north-westwards from lat. 1° N. and long. 38° E. to within a short distance of Lake Rudolf. Eastwards the Coastal Belt of sediments proved to be of Upper Oxfordian age and to extend to long. 403° KE. (west of Hil Wak), and these were lost southwards under the great alluvial plain of Jubaland.
At intervals throughout the alluvial plain ard lying in hollows in the Jurassic rocks, disconnected exposures were found of soft calcareous sandstones or limestones (Wajhir, Eil Wak), the age of which cannot now be definitely fixed.
Evidences of the desiccation of the country were, it was thought, shown (1) by the Laks or. water-channels characteristic of Jubaland, which contained surface-water only during the rainy season and then
Reports & Proceedings—Geological Society of London. 43
extremely rarely, if ever, throughout their length; (2) by the presence of freshwater molluscs in the scarcely consolidated beds of such Laks and at other places where now no surface-water is present (Buna and near the Abyssinian frontier); and (3) by the presence of wells along fault-lines and in other places where, but for the previous presence of springs, it appears improbable that the natives would have begun sinking.
The region between Lake Rudolf and Marsabit was pointed out as one of exceptional interest, which the speaker had so far not been able to investigate.
The depression between the Mathews and associated ranges and the Abyssinian frontier on which the Marsabit and Hurri volcanoes were situated, and the origin of the Kuroli Desert (Elgess), were the outstanding features of the district that required further elucidation.
Mr. G. C. Crick stated that the Cephalopoda submitted to him by Mr. Parkinson consisted chiefly of crushed ammonites from dark-grey shales at Kukatta on the Juba River (lat. 2° 8’ N.), there being also a belemnite preserved in a yellowish-brown rock-fragment from Serenli on the same river and somewhat north of Kukatta. He concluded that the shales at Kukatta were of Upper Oxfordian (Sequanian) age.
Mr. R. Bullen Newton had examined a small series of non-marine
»Kainozoic molluscan remains belonging to recent species, and associated with hard and soft limestones, calcareous sandstones, and conglomerates, which had been collected by Mr. Parkinson, and had determined about nine genera and twelve species. No vertebrates
- occurred with these shells, hence their age would probably be younger than the Omo-River deposits north of Lake Rudolf, and that yielded a somewhat similar molluscan fauna, but with the addition of Dinotherium and other vertebrate remains. The presence of that genus, as pointed out by Dr. Haug (Zraité de Géologie, 1908-11, vol. ii, p. 1727), was indicative of the Pontian or Upper Miocene Period. There are, however, some lacustrine beds near Lake Assal, in French Somaliland (formerly regarded as Abyssinia), which contain shells also bearing a resemblance to those collected by Mr. Parkinson in British East Africa, especially MMelania tuberculata, Cleopatra
bulimoides, Corbicula fluminalis, and C. radiata, which are common to both sets of deposits. These Lake Assal beds, which are also without vertebrate remains, have been identified by Aubrey (Bull.
Soc. Géol. France, ser. 11, vol. xiv, pp. 206-9, 1885), and Pantanelli (Atti Soc. Toscana Sci. Nat. Proc.-verb., vol. v, pp. 204-6, 1887,
and ibid. vol. vi, p. 169, 1888) as of Pliocene age. If, from these facts, such widely distant beds can be recognized as contemporaneous, then the suggestion may be made that the northern half of British
East Africa was probably an extensive freshwater region during Pliocene times, limited on the north by Lake Assal, on the east by Suddidima, on the south by Archer’s Post and the Mount Kenya plateau, and on the west by Lakes Rudolf, Stefanie, and Marguerite.
Assistance in the determination of these shells had been kindly rendered by Mr. E. A. Smith, 1.8.0.
+4 Reports & Proceedings—Mineralogical Society.
2. December 1, 1915.—Dr. A. Smith Woodward, F.R.S., President, in the Chair.
The President exhibited lantern-slides lent by Professor Elliot Smith to illustrate the fossil human skull found at Talgai, Darling Downs, Queensland, in 1914. The specimen was brought to the notice of the British Association in Sydney by Professor T. W. Edgeworth David, and would shortly be described by him and Professor Arthur Smith. It was obtained from a river-deposit in which remains of Diprotodon and other extinct marsupials had already been discovered, and there could be no doubt that it belonged to the Pleistocene fauna. It therefore explained the occurrence of the dingo with the extinct marsupials. The skull is typically human and of the primitive Australian type, but differs from all such skulls hitherto found in possessing relatively large canine teeth, which interlock like those of an ape. The upper canine shows a large facet worn to its base by the lower premolar. The discovery of the Talgai skull is, therefore, an interesting sequel to that of Mr. Charles Dawson’s Piltdown skull, in which the canine teeth are even more ape-like.
Dr. J. W. Evans discussed the different methods of obtaining the directions-image (‘‘interference figures’’) of a small mineral in © a rock-slice, unaffected by the light from neighbouring minerals. He preferred the use of a diaphragm in the focus of the eye-piece, in conjunction with a Becke lens.
He also described the inferences that might be drawn from the ~ form, position, and movement on the rotation of the stage of the isogyres (dark bars or bushes) in the directions-images, both of chance sections and those cut parallel to planes of optical symmetry or at right angles to optical axes. He showed how the character or sien of the crystal and its approximate optic axial angle might be determined.
IIT.—Mineratoeicat Sociery.
Anniversary Meeting, Movember 9, 1915. W. Barlow, F.R.S., President, in the Chair.
W. Barlow: Crystallographic relations of allied substances traced by means of the law of valency volume. ‘The ordinary parameters of a crystal do not necessarily express the actual ratio between the minimum translations of the crystal structure, and it is justifiable to multiply one or sometimes two of them by a small integer in order to obtain the equivalence parameters. A number of cases were taken which showed that in crystals which either contain the same radicle or closely related radicles the similar parts are arranged in identical strata intercalated between the remaining constituents of the crystal. A. F. Hallimond: On Torbernite. From measurements made on several specimens the axial ratio a: ¢ = 1: 2'947 was determined, and the forms 001, 101, 108, 111, 112, besides vicinal faces, were observed. The mineral becomes unstable at vapour-pressures about one-third that of water, and passes into Rinne’s meta-torbernite I. At higher temperatures the transition-curve rises sharply, and meets the vapour-pressure curve of water at 75° C., above which torbernite has no stable existence in air. T. V. Barker: On the solution
Correspondence—Bernard Smith. 45
of the problem of Four Tautozonal Poles. The indices of two poles C, D may be expressed as functions of those of the two other A (adc), B (def) in the form (pa+qd, pb+-ge, pe+ qf), (ma+nd,mb+-ne, me+nf) where p, g, m, m are small positive or negative integers. Since npcot A D=(np-mq)cotAB+mqcot AC, a table of natural cotangents enables a numerical example to be solved rapidly. Usually p=q=1, and the equation reduces to ncotAD=(n-m)cotAB-+ mcot AC. L. J. Spencer: Crystals of Iron Phosphide (Rhabdite) from a Blast- furnace. The small, acicular, tin-white, and strongly magnetic erystals were found sparingly in cavities in a large mass of metal at the bottom of a blast-furnace near Middlesbrough. They are tetragonal (sphenoidal -hemihedral) with the axial ratio, -@:c=1:0°3469. Dr. G. T. Prior: The Meteoric Stone of Cronstad Orange Free State.
At the above meeting the following officers and members of Council were elected: President, W. Barlow, F.R.S.; Vice-Presidents, Professor H. L. Bowman and A. Hutchinson; Treasurer, Sir William P. Beale, Bart., K.C., M.P.; General Secretary, Dr. G. T. Prior, F.R.S.; Foreign Secretary, Professor W. W.- Watts, F.R.S.; Editor of the Journal, L. J. Spencer; Ordinary Members of Council, Dr. J. J. Harris Teall, F.R.S., F. N. Ashcroft, Professor H. Hilton, Arthur Russeli, W. Campbell Smith, Dr. J. W. Evans, Dr. F. H. Hatch, J. A. Howe, T. VY. Barker, G. Barrow, Dr. C. G. Cullis, and F. P. Mennell.
CORRESPON DHNC#.
‘ON CERTAIN CHANNELS.”
Srr,—A section of Professor Bonney’s recent essay On certain Channels attributed to overflow streams from ice-dammed lakes! is devoted to an extremely courteous criticism, but final rejection, of _ my interpretation of glacial phenomena in the Black Combe area.’ Since he advances an alternative hypothesis to account for the above- mentioned channels, [ am sure he will pardon me if I, in my turn, offer a few critical remarks.
I must first protest against Professor Bonney’s assumption (vede title of his paper) that I ascribe practically all these channels to overflow waters from ice-dammed lakes. In many cases, as I clearly state, they were merely carriers of the normal marginal drainage of an ice-sheet. Nor do I invent ice-dams ‘‘almost by the dozen’’. As regards overflows from lakes, one dam—the Irish Sea Ice—is quite sufficient.
In my description the drainage channels are discussed and ' interpreted in the light of observations, recorded on 6 in. field maps, and fall into place as an important chapter in the glacial history of the area. Professor Bonney states that he accepts most of my facts, but differs from my conclusions; yet, having made this admission, and agreeing that land*ice ‘‘occupied all this district during some part of the Ice Age’’, he appears to ignore the evidence
1 Published by Bowes & eae Cambridge, 1915. 2 Q.J.G.S., vol. Ixviii, 1912.
46 Correspondence—Bernard Smith.
relating to the composition, character, and location of the glacial drifts, as well as that furnished by erratics, ice-moulded surfaces, and strie.
Having thus divorced these anomalous channels from their surroundings, he has constructed a theory to explain their origin (as it seems to me) based chiefly upon their shape and rate of fall.
If land-ice ‘‘ occupied all this district during some part of the Ice Age’’, and there was no Irish Sea Ice, I venture to ask why (as its markings show) the ice from Eskdale first turned south, along the seaward slope of Black Combe, and then swung to the east and north- east into the mouth of the Duddon estuary; and why the Whicham Valley Ice, moving first in a south-westerly direction, was also directed towards the south-east and east near the mouth of that valley? Why did it not ride out to sea? What was the impelling force that turned it aside ?
Professor Bonney doubts whether marginal streams could cut channels in granite in a short time. He may read of recent examples described by Von Engeln,' to whose article I have already made reference.
My critic admits that the systems of parallel trenches on the west coast, as contrasted with the preglacial drainage, are abnormal in direction, and finds some difficulty in explaining this anomaly, but confesses himself happier when dealing with the channels east of Black Combe, where ‘‘the trenches take a more normal course’’. The explanation issimple: in the first case the trenches were marginal to the Irish Sea Ice, and are therefore transverse to the normal drainage, whereas in the second case they were marginal to the local | Lake District glaciers which occupied the present drainage lines at a late stage of the glaciation. If, as Professor Bonney maintains, the dry channels on the west coast are preglacial, how does he explain the presence of thick glacial drift upon the ground between them, and upon the higher inland slopes, but not within them ?
Perhaps the weakest part of this new hypothesis is an attempt to explain the ‘in-and-out’ channels by marine erosion of the seaward wall. A preglacial submergence cannot be invoked, because one of the long ‘in-and-out’ channels (Monk Foss) is cut entirely in glacial drift; nor can we admit a postglacial submergence, for that would have entirely destroyed the typically hummocky character of the drift on the plain between Millom and the mouth of the Esk. Moreover, even were ‘in-and-out’ channels at this spot due to marine erosion, we cannot explain in this manner the ‘ in-and-out’ channels of other districts far from the sea.
Finally, one might pertinently ask how pre-Triassic valleys could have maintained such sharp well-defined contours to this day. As a field-geologist I have frequently noticed the “‘ half effaced features of an earlier topography ’’, but in few instances have I seen anything more blatantly modern in appearance than these marginal or overflow- channels in the Black Combe district, or, indeed, in North Wales, where they are cut in fairly soft shales.
1 “Phenomena associated with Glacial Drainage and Wastage’’: Zeit. Gletscherkunde, vol. vi, pp. 126-31, 1911.
Correspondence—Prof. T. G. Bonney. 47
This conception of old drainage systems running parallel to the contours of the mainland, in Cumberland, Haddingtonshire, S.E. Ireland, Denbighshire, Flintshire, etc., when coupled with the warping movements necessary to explain the steep fall of the channels, sets the mind, no less than the land, awhizrl.
BERNARD SMITH.
THE GEOLOGICAL AGE OF THE CARRARA MARBLES.
Sir,— Permit me to comment briefly on Dr. Du Riche Preller’s paper on the Carrara Marble District.1 It contains a quantity of interesting information, topographic and economic, but does little, in my opinion, to settle the question as to the age of those rocks or strengthen the position of the Italian geologists. I had their map with me in the autumn of 1889, and in regard to faults (which Dr. Preller considers to be almost negligible) wrote thus in my diary: ‘‘ In order to accept the geological succession they have indicated, we must explain the proximity of ordinary dark mechanically disturbed limestone (just like some of that at Spezzia) with lighter varieties to perfectly typical Carrara marble.” I was aware that the statuary marble is intercalated with marbles of inferior quality, but instead of finding any sign that the metamorphism was a result of pressure, maintain that, as shown by the microscope, that marble has escaped (as I stated) from the crushing which has affected its associates. As to ‘metamorphism’ and its effect on sedimentary rocks, I have been doing my best to study the whole question since about 1875, have spent much time and money in examining alleged passages from crystalline schists to comparatively unaltered sediments or intercalations of the two, with the invariable result that the evidence was never conclusive and very commonly worthless; in fact, I have not been able to discover any case (I have not restricted myself to the Alps) where a truly crystalline limestone, such as that of Carrara, is in stratigraphical sequence with a sedimentary rock to which a date ‘can be assigned on the evidence of fossils, except in the case of contact metamorphism, which, so far as I am aware, is not exhibited in the Apuan Alps. Dr. Preller’s paper contains no evidence that he has made use of the microscope in studying these Carrara rocks, and as I know the vague use of the term ‘schist’ by many Continental and some British geologists I am unable to discuss his sections (Figs. I-LV) beyond saying that only one of them seems to demand an explanation, and this I think my past experience would enable me to
supply. T. G. Bonney.
RENE ZEILLER—MASTER PALHOBOTANIST.
Sir,—In the current number of ature there is a short tribute by Professor Seward to Professor Zeiller, whose death this week in Paris we all deplore. I should like to add a word in token of the deep and lasting affection and reverence the great Palzobotanist inspired in his younger colleagues in many countries.
*1 Grou. MAG., December, 1915, pp. 554-65.
48 Ohituary—Arthur Vaughan.
Long before I had personally met him, his work, so deep, so wide, so balanced, so exceptionally thorough, had proclaimed him to me as the master paleobotanist of our time. Professor Seward has referred to his magnificent memoir on the fossil flora of Tonkin: it is, I think, the most perfect piece of paleobotanical work extant—the most perfect in not only containing conclusions of far-reaching and profound significance, but in being the freest from the minor defects of misapprehensions, ‘of carelessnesses, misquotations, and incomplete or incorrect references which are present in nearly all work and abound in some.
It was on visiting Professor Zeiller in Paris, however, that the full extent of his work became apparent tome. The wonderful collection of fossil plants which he had brought together and so intimately knew is, in some respects, unsurpassed and is invaluable to students. Then, too, Professor Zeiller held a unique position in relation to practical mining, and was the guide, philosopher, and friend of Government Departments and coal-miners in a way which is almost unimaginable in this country, where palzobotanists are held in little honour and are put to little practical use. His prescience, based on detailed paleeobotanical knowledge, saved his country many tens of thousands of pounds.
But surpassingly in Paris did the enchanting personality of the great man become apparent. Unique were his cenerosity, his sincerity, his aristocratic and beautiful courtesy and heipfulness towards the younger workers, at whose service he placed the whole storehouse of his profound and well-balanced knowledge. Even in Berlin, where I have heard nearly every other paleobotanist roundly abused, Zeiller —Frenchman though he was—was spoken of with affection and respect.
It is due only to the fact that Professor Zeiller worked in the
-* Cinderella’ science. of paleobotany instead of in some popular and widely respected science like chemistry that his death is not universally hailed by the general public as the irreparable loss it is. To us who knew and loved him, as to his colleagues all over the world, no one can replace René Zeiller.
Marte C. Sores, Lecturer in Palzeobotany, University College, Roden 14 WELL WALK, HAMPSTEAD HEATH, N.W. December 10, 1915.
(SpSneAGoyya IS, N ee
ARTHUR VAUGHAN, M.A., D.Sc., F.G.S., Lecrurer In GEroLocy oF THE University or OxrorD. We regret to record the death of Dr. Arthur Vaughan, which occurred on Friday, December 8, 1915, at 315 Woodstock Road,
Oxford, in his 47th year. We hope to give a notice of his geological work in the next number of the Magazine.
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IT, ORIGINAL ARTICLES. Page Il. REVIEWS. Page On Saurostomus esocimus, Agassiz. Geology of To-day. By Dr. J. W. ByA. SMITH WOODWARD, hi 1D Gregory, I'.R.S. Peters Oh F.R.S. (PlateII.) .. .. 49 | Stegocephalia of Senekal, O.F.S. i By Dr. EH. C. N. van Hoepen ... 83 The Punctation of Terebratulid J. ; s Shells. By F. G. Purctvat, ae Economic ee Canada 87 “B.Se., F.G.S. (Plate III atid sostasy and Radioactivity. By 2 Text-figures.) ... ii eRe ESO 1 G. F. Becker... 88 iy Besse oe ‘ | The Klondike and Macon Goldfield 89 er The Fluvio-glacial Gravels of the The Mineral Resources of the ' Thames Valley. By R. M. Philippines LOU i ee os 89 DEELEY, M.Inst.C.H., F.G.S. Lavas of Hawaii. By W. Cross... 89 (Plate Bes. 57 | Wabana Iron Ore, Newfoundland. ~The Eocene of Tete ‘By I RENE 63,7 By A. O. Be ste et AO) FourtTau, Member of Heyptian BN aes ia 8s 90 TE SEIURE 2 - Ill. REPORTS AND PROCEEDINGS. eee for, Wator at Hinckley, ae Liverpool Geological Society 90 Calcium Carbonate and Evolution 2 ue SUP BET SD ENG. 2 in Polyzoa. By’ W. D. LANG, C. S. Du Riche Preller ... 92 fae M. A., ie G. Ss. ints . 73 We OBITUARY. Glacier Lake Gigi ne Pia Dr, Arthur Vaughan, M.A. (P1.V.) 92 fessor PERCY FRY KENDALL. Dr. J. C. Moberg ia ee OO (With a Text-figure. we .. 77 | W. Rupert Jones 96
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THE IRON ORE RESOURCES OF THE “WORLD.
A Summary compiled upon the initiative of the Executive Committee
of the Eleventh International’ Geological Congress, Stockholm, 1910,
with the assistance of Geological Surveys and Mining Geologists of different Countries.
EDITED BY THE GENERAL SECRETARY OF THE CONGRESS.
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CLIMATIC CHANGES SINCE THE LAST ICE AGE.
A Collection of Papers read before the Committee of the Eleventh. International Geological Congress at Stockho/m, 1910.
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GHOLOGICAL MAGAZINE
NEW SERIES. DECADE VI. VOL. Ill. No. II.—_ FEBRUARY, 1916.
ORIGINAL ARTICLES.
I.—On a New Specimen oF tHE Liassic Pacnycormip FIsH SAUROSTOMUS ESOCINUS, AGASSIZ.
By A. SMITH WOODWARD, LL.D., F.R.S., Pres. Geol. Soc. (PLATE II.)
LTHOUGH the Pachycormid fish Saurostomus esocinus was A known only by part of a lower jaw from the Upper Lias of Baden when it was first named by Agassiz, its principal characters have since been revealed by many incomplete specimens from the Upper Lias of Wiirtemberg, France, and Yorkshire, and by a well- preserved fish from Ilminster, Somersetshire, in the Charles Moore Collection, Bath Museum.! The internal skeleton of the trunk and the fins, however, have not hitherto been so well seen as in a nearly complete fish from the Upper Lias of Wiirtemberg, prepared by Mr. Bernhard Hauff and now in the British Museum.
This new specimen, which measures about 1:4 m. in total length, is shown of about one-eighth the natural size in Plate II. The head is deepened by crushing, so that the roof is pushed upwards above and ‘the gular plate downwards below ; but it is obviously shorter and wider than that of Pachycormus, while the snout is comparatively blunt. The external bones are thin and of fibrous texture, and are thus crushed on the stouter inner elements in a confused mass, but - afew features are recognizable. A notch in one bone which seems to be nasal may be regarded as marking the narial opening. The blunt rostral region is shown in front view, with a row of small conical teeth along the oral border as already observed in a Whitby specimen. The large orbit is indicated by an ossified sclerotic in two halves, anterior and posterior. The cheek-plates are obscured by their crushing on the mandibular suspensorium and pterygo-palatine bones; but it is clear that although the hyomandibular is inclined backwards, the quadrate turns as sharply forwards, so that the mandibular articulation is not far behind the orbit. Below the cheek the long and slender maxilla is conspicuous, a little downwardly curved in its hinder portion, where its upper border is overlapped by a single long and narrow supramaxilla. The maxilla bears the usual large conical teeth in a spaced series, flanked outside by a close series of comparatively minute teeth, as in Hypsocormus. A cluster of rather large teeth, of the palatine or other inner element, is also seen between the maxilla and displaced premaxilla. In the mandible the
1 For references to literature see Catal. Foss. Fishes Brit. Mus., pt. iii, p- 388, 1895; also A. S. Woodward, ‘‘ Fossil Fishes of the Upper Lias of Whitby,’’ Proc. Yorks. Geol. and Polyt. Soc., vol. xiii, p. 158, pl. xx, 1896.
DECADE VI.—VOL. II.—NO. II. 4
50 Dr. A. Smith Woodward—On Saurostomus esocinus.
angular bone is relatively small, and the dentary is as originally described by Agassiz. The lower teeth of the spaced series are slightly larger than those of the upper jaw, but are similarly flanked . outside by clustered minute teeth. All the teeth are conical, a little incurved at the apex, covered with smooth enamel, and: vertically fluted at the base. The preoperculum, operculum, and suboperculum are vaguely seen, of the characteristic shape. Behind the large gular late there are also traces of the branchiostegal rays.
The trunk is distorted as usual, especially just in front of the dorsal and anal fins, which are thus separated a little from their supports. The vacant space for the notochord is widened by this distortion, but most of the arches above and below are well preserved. The total number of vertebral arches is about 110, of which 50 may be assigned to the abdominal region. The ribs are comparatively short and slender, while the neural arches of the abdominal region bear gently curved spines, each forming an irregular node at its fused lower end and tending to slight expansion at its upper or distal end. In the caudal region the simple neural and hemal arches are nearly symmetrical above and below the notochordal space, and sharply inclined backwards. Within the base of the tail six or seven hemals become relatively stout, and the last hemal forms the fan-shaped bone which is so characteristic of the Pachycormide.
In the pectoral arch the two supraclavicles are well seen, relatively large, long and narrow, straight, and of conspicuously fibrous texture. The clavicle is obscured, but behind it there are traces of the usual thin and large postclavicular scales. The right pectoral fin is specially well preserved, with at least twenty rays, which do not appear to be transversely articulated but become very finely divided distally. The fourth or fifth and longest ray is gently curved and much longer than the others, which rapidly shorten backwards.’ There is no trace of pelvic fins. The supports of the dorsal and anal fins, which are well preserved though displaced, are remarkable for their great length. Not less than twenty-five or twenty-six of these supports are shown in each fin, all expanded at the end for articulation with the fin-rays. The dorsal fin must have been almost completely in advance of the anal, and the fragmentary remains show that it was elevated in front, comparatively low behind. The anal fin is altogether less elevated, and the articulations of its rays are shown to have been distant. The rays of the powerful forked caudal fin are also articulated only at distant intervals, but are very finely sub- divided distally.
Nearly all the scales have been removed from the fossil, but a scattered patch behind the dorsal fin shows that they are small and thin, with some traces of a very fine tuberculation. There are vague remains of the enlarged scale at the origin of the anal fin. Indications of digested food are also seen in the abdominal region.
The most interesting feature of this new specimen of Sawrostomus is the remarkable elongation of the anterior pectoral fin-ray, which
1 The pectoral fin from Whitby figured in Proc. Yorks. Geol. and Polyt. Soc., vol. xiii, pl. xx, fig. 2, 1896, thus seems to belong to Pachycormus, not to Saurostomus.
‘mo 69 X ZL 9ZIS “YeN ‘NUGVNZ1IOW *‘SyIT] Utdd{) ‘zusspby ‘SQNTOOSH SONOLSOUNYVS
‘TI divIg ‘QIGL “PVIN “10s
F. G. Percival—Punctation of Terebratulid Shells. 51
suggests its use as a tactile organ. Although stich elongation is not uncommon among modern Teleostean fishes, it does not appear to have _ been observed hitherto among Mesozoic Ganoids. I may also add that some of the bones, such as the supraclavicle and the neural arches fused with their curved spines, are exact miniatures of some of the bones of the gigantic Leedsia problematica from the Oxford Clay. They therefore tend to support the opinion that this largest known Mesozoic Ganoid belongs to the Pachycormide. EXPLANATION OF PLATE II.
Saurostomus esocinus, Agassiz; nearly complete fish, about one-eighth natural size. Upper Lias: Holzmaden, Wiirtemberg. British Museum No. P. 11126. Prepared by Mr. Bernhard Hauft.
Il.—On tHe Poncrarion oF THE SHELLS or ZeRERRATULA. By F. G. PERCIVAL, B.Sc., F.G.S., Assistant Lecturer in Geology at the University of Manchester. (PLATE III.)
ile 1844 Carpenter [1] divided the fossils then known as Zerebratula
into two groups—a perforate group, having the test covered with ’ minute pores, and an imperforate group (the Rhynchonellids). These perforations (see Plate III) correspond to tubular processes of the mantle.
Sharpe [2] suggested that these cecal processes of the mantle had a respiratory function; but the shell is covered with a chitinous periostracum which is imperforate. Carpenter considered this might be cellular, allowing water to pass through. Sollas [3] in 1885 suggested that they were sense organs affected by light, since the - periostracum is transparent. Morse [4] offers the suggestion that they are organs of general sensibility.
The tubules are not of uniform diameter throughout. The inner half, near the mantle, according to King [5] is narrow, the outer half wider, with a sudden dilation at the ‘mouth’. From the mouth a number of fine lines or tubes radiate. It is interesting to note that from the outer lip of each cecal process a number of fine cilia radiate. Possibly these cilia fit into the radiating tubes (see Morse [4]). The radiating tubes are rarely seen in fossils. An example is shown in Pl. III, Fig. 3.
In some forms, e.g. 7. punctata, Sow., the puncte are elongated and slit-like at the outer surface, but have a round cross-section a little farther in. This is well shown in Fig. 5, where part of the outer layer has flaked off.
In Zerebratulina (Fig. 1) the cecal tubules branch as they pass outwards, but I have not observed this in any species of Zerebratula. It would, however, be difficult to recognize in fossil specimens, even if present.
The examination of the puncte, or external openings of the tubules, was first undertaken ‘with the hope of using their variations as aids in distinguishing species. The puncte are arranged in rows roughly parallel with the growth-lines. When the apertures are slit-like the long axis of each slit points to the umbo, and this emphasizes the fact that they are also arranged in rows radiating out from the umbo.
52 F. G. Percwal—Punctation of Terebratulid Shells.
Where the shell is smooth one may find either a square or a quin- cuncial pattern, but this regularity is broken by the subdivision of the rows, both transversely and radially. There is a tendency here and there for the lines to become very irregular, the radial rows ‘streaming out’ into many branches. This occurs, Mr. J. W. Jackson informs me, particularly along the muscle impressions. In the gerontic stage the transverse lines are no longer in sweeping con- tinuous curves, but are broken up into many little wavelets, and it is very difficult to count them.
With regard to the size of the puncte, one can distinguish roughly between coarsely and finely punctate shells, but nicer distinctions are unreliable, since the shapes of the individual puncte depend very largely on the amount of wear the shell has suffered; e.g. in T. punctata, Sow., an unworn shell may show long slit-like puncte, while a more worn test has rounded pores. Usually the puncte are hollows, but in specimens that have been naturally etched the material filling the puncte may project beyond the general surface level. Sometimes the ‘walls’ of each punctation project slightly, forming a small tube-like process. But all these differences may occur in one species, or even in different parts of one individual, and are therefore useless for our purpose.
The only other convenient means of distinction by puncte is the variation in the number per square millimetre (or ‘density’). If the various species have sufficiently different densities this would be a valuable aid in specific determination. It is already so used to some extent."
There is a gradual increase in the density from the umbo outwards to the anterior edge. The following readings are typical—
T. biplicata (Brocchi) (a) 93, 111, 115, per sq. mm. (6) 72, 75, 86, 98, per sq. mm. (c) 68, 62, 81, 92, 112, per sq. mm. (d) 49, 54, 67, 90, per sq. mm.
T. aff. crickleyensis, 8. Buckman, 224, 292, 344, per sq. mm.
In each of the above five examples the first reading was at about 1:5 cm. from the umbo, the other numbers being progressively farther out. Not all of the individuals show such big variations, and. this increase is not always regular. Occasionally there will be a decrease in: density over a zone a few millimetres wide (see example ¢ above). Again, when a strongly marked growth-line intervenes there is usually a sudden change of density. This is to be expected if there is a continuous variation from youth to age, a variation which is maintained even during the period of slow growth or cessation of growth represented by such a strongly marked growth-line. In 7. diplicata (Brocchi) the rate of increase is more rapid towards the sides than towards the anterior along the median line. This is obviously because the shell is longer than it is broad; hence growth takes place more rapidly at the anterior edge than at
1 See e.g. F. Blochmann, Die Brachiopoden der Schwedischen Siidpolar- expedition, Stockholm, 1912, and J. W. Jackson, ‘‘ The Brachiopoda of the Scottish National Antarctic Expedition ’’; Trans. Roy. Soc. Hdin., vol. xlviii, pt. ii, No. 19.
F. G. Percwal—Punctation of Terebratulid Shells. 538
the sides, and one travels over the stages from youth to age more quickly in an oblique direction than along the median line. The variation is negligible along any particular zone of growth parallel to the growth-lines.
It follows from the foregoing that one must always choose some fixed part of the test for the counting. In the earlier work the valves were divided into squares of one centimetre, commencing at the umbo, the lines being painted in water-colour. Readings were taken in the second square, i.e. at between one and two centi- metres from the umbo, on the dorsal valve when possible, otherwise on the ventral. The figures for the ventral valve are approximately the same as for the dorsal.
If the density'is to be of any value the range for a species must not be very great. But it appeared in one or two cases that there was a rather large variation. Moreover, as previously mentioned, occasionally a sudden change occurred. For example, a specimen of Microthyris sublagenalis, Davidson, showed in the first square centi- metre a band where the density rose suddenly from 168 to 272 (see Pl. III, Fig. 2). A strong growth-line separated the two readings, but farther out, in the third square from the umbo, the density had fallen to 152. Obviously, if irregular variation like this is at all common there will be a big range for each species, even if we confine our readings to a spot of very small area at a fixed distance from the umbo in each example.
In order to test this large numbers of two species were collected. The first was 7. beplicata “(Brocchi), using the term in Davidson’s broad sense, of which 166 examples were obtained from the Manchester Museum collection. All were from one horizon and loeality—Lower Chalk, Sewell. There was a fairly wide variation in form, but there was a complete gradation among them. Over 300 specimens of 7. punctata, Sow., were also collected from a couple of blocks in a Middle Lias quarry at Stathern, Leicestershire. In these specimens the puncte were usually beautifully preserved and yet difficult to count. Staining did not improve them at all. Most of them had transparent shells with a black matrix inside and filling the puncte. The matrix showed through the test, and the puncte were almost invisible against the dark background. On heating the fossils on wire gauze over a Bunsen flame the tests cleaved into myriads of tiny rhombs, giving an opaque white appearance against which the black puncte showed very distinctly. After heating, the surface was covered with Canada balsam to prevent flaking, but in some cases it was an advantage to let the thin outer layer flake off, as the round cross-section of each punctation in its inner half made a very distinct spot, easy to count.
At first photomicrographs of known magnification were taken, but this was too slow a process. The later work was done by using a long extension camera, giving» an image magnified fourteen diameters. A square of 14 millimetres was cut out of a sheet of paper, which was then moved into various positions on the screen. With the aid of a lens several readings were thus taken for each individual, by counting the numbers in the square. These readings
54 F. G. Percival—Puncetation of Terebratulid Shells.
were averaged. In order to keep approximately to the same area in each case a circle was drawn on each specimen.
The range in each of the two species was very great. There is no reason to suppose that they are in any way abnormal. In 7. biplicata one individual had a density of only 39 per square millimetre, and one was as high as 129. 7’. punctata ranged from 66 to 240. Thus these two species alone cover a great part of the whole range of variation possible for the genus, and the feature must be of extremely little value for purposes of specific distinction. The following tables summarize the results. It was necessary to group the density numbers in tens for two reasons: first, the actual number of individuals was small compared with the great amount of variation, and secondly, certain numbers tended to predominate owing to the method of counting. In order to count accurately from 100 to 200 tiny spots within a square of 14 millimetres one must, if possible, get them arranged in rows parallel with the sides of the square. As a result one often gets, say, eight rows of eight or nine puncte, and so on; i.e. numbers like 64 (8 X 8), 72 (8 xX 9), _ 81, 90, 100, 121, etc., will unduly predominate. So those individuals
with a density of from 41 to 50 were grouped together, and so on.
TABLE I.—T. pwnctata. (See Fig. 1.)
Puncte per sq. mm. Nos. of individuals. 61- 70 5 6 5 js . 5 ; ih 71-— 80 0 a 4 : : ; : 3 81- 90 A ° 6 : B : 0 9 91-100 : 5 5 5 : : : 19
101-110 i 3 : ‘ 5 : 6 32 111-120 A 3 0 i 7 5 6 56 121-130 6 fs 5 is - a , 56 131-140 . A 2 ; 5 A c 46 141-150 3 6 : , 5 * fe 44 151-160 . . $ 3 : & é 41 161-170 5 5 ¢ A 6 i 27 171-180 ‘ s : é : a A 11 181-190 : 5 - 4 - : 7 191-200 A F 3 ‘ 4 201-210 4 211-220 : A é é ; : si 4 221-230 5 3 : 6 , : 3 2 231-240 ili
Total . 5) BT
TABLE II.—T. biplicata. (See Fig. 2.)
Puncts per sq. mm. Nos. of individuals. 31- 40 i iB 5 c $ A ; 1 41- 50 é é 6 5 s 4 ; 13 51- 60 4 5 5 3 5 4 36 61-— 70 : 3 : : 3 : se 413} 71- 80 b z i ; ‘ ; 41 81-— 90 6 ‘ 3 é i : 5 14 91-100 4 : A 5 3 é 10
101-110 3 x A ‘ : s ‘ 6 111-120 F A i 4 : A 1 121-130 A . 5 5 , 4 4 ih
Total ‘ = 6G
F. G. Percival—Punetation of Terebratulid Shells. 55
The results are shown graphically in Figs. 1 and 2. It will be seen that the curve for 7. biplicata is a simple variation curve, confirming the fact that only one species was being dealt with, and incidentally supporting Davidson’s application of the name to a wide range of forms. The mode occurs at between 60 and 70 per square millimetre. The curve for Z. punctata shows a fairly pronounced hump a little beyond the mode, which lies between 110 and 130.
Fie. 1.
6 setae ae t s ae ~ 50 .70 90 uo 13Q 450 170 190 210 230 250
30
20
0
30 40 50 60 70 60 90 100 “1a 120 (30
Fie. 2.
Fic. 1.—Curve showing variation in number of puncte per sq. mm. in 367 individuals of J. punctata, Sby. Abscisses = puncte Be: sq. mm. Ordinates = numbers of individuals.
Fic. 2.—Curve showing variation in number of puncte per sq. mm. in 166 individuals of T. biplicata.
56 F. G. Percival—Punctation of Terebratulid Shells.
This may imply the oncoming of a variation, but possibly it may mean that the mode of the specimens from this locality was a little lower than the mode for the species as a whole. If, for example, the mode for the whole species were 150, and the mode for this particular locality between 110 and 130, one would expect the numbers of individuals with a density of 130 to 150 to be greater than those with density 110 to 90, i.e. the curve would slope down more gently to the right of the mode than to the left.
In conclusion three points may be emphasized: (1) The shapes of the individual puncte depend to a great extent on the state of preservation of the test, since the shape of the cross-section of a punc- tation often varies as it passes outwards, from circular to oval or slit-like. (2) There is in general a progressive increase in density from the umbo outwards, which is approximately the same in each valve. This increase is not always regular; occasionally the density will decrease for a while, and at the larger growth-lines there is usually a sudden increase. (3) The amount of variation in a species is so great as to make the density almost valueless as a specific character.
I wish to offer my grateful thanks to Dr. A. Morley Davies, Dr. G. Hickling, and Professor H. H.Swinnerton for the advice and help they have given at various times during the rather tedious work on which this paper is based.
EXPLANATION OF PLATE III.
Fig. 1. Dyscolia crossei, Day. Recent: Japan. Middle of ventral valve photographed from outside, showing branching punctations. The forks point to the umbo. (This is the case in all Terebratuline I have examined, though Fischer & (hlert, in describing this species, state that the canals are directed obliquely ‘‘ d’arriére en ayant .)) x 485
», 2. Microthyris sublagenalis, Day. Bathian: Marquise, Boulonnais. Dorsal valve, less than 1 em. from umbo, showing a sudden increase of density from 168 to 272 per sq. mm. x 20.
», 3. LT. punctata, Sow. Middle Lias: Stathern, Leicestershire. Portion
‘ of test showing ‘‘radial canals’’ at outer aperture of each punctation. x 40.
» 4. TL. punctata, Sow. Flake of shell by transmitted light, showing puncte with circular cross-section, changing to slit-shape at the outer surface. x 40.
» oO. TL. punctata, Sow. Test by reflected light. A thin outer flake is removed to show the round section of each punctation towards the inner surface of the test. x 14.
REFERENCES.
1, CARPENTER (Dr. W.). ‘‘On the Microscopic SUN: of Shells’’: Rep. Brit. Assoc., 1844, pp. 16-18.
2. SHARPE (Daniel). ‘‘On Trematis’’: Q.J.G.S., Fol: iv, p. 67, 1848.
8. SoLuas (Professor W. J.). ‘‘ Notes on the Cxcal Processes of the Shells of Brachiopoda interpreted as sense-organs’’: Sci. Proc. Roy. Dub. Soc., N.S., vol. v, 1886-7.
4, Morse (E.S.). ‘‘On the Embryology of Terebratulina’’: Mem. Boston Nat. Hist. Soc., vol. ii, 1871-8.
5. KiNG (Professor W.). ‘‘ On the Histology of the Test of the Class Pallio- branchia ’’: Trans. Roy. Irish Acad., vol. xxiv, p. 439, 1867.
Grou. Maa., 1916. Pratm IIT.
oa: ate figs ts
4
Bs ey 3 ‘ bg C9 itt tT, aw» iM its
TEREBRATULID SHELL-STRUCTURES.
. ; Lad ; f M ; 3 : fy ej “4 ~ u ‘ : 1 ! F ; ;
R. M. Deeley—The Thames Valley Gravels. 57
IJ1.—Tar Frouvio-etactan GRAVELS oF THE THAMES VALLEY. By R. M. DEELEY, M. Inst.C.H., F.G.S. (WITH A FOLDING MAP, PLATE IV.)
CAREFUL examination of the distribution of the high-level gravels and sands of the Thames Valley, especially those associated with the boulder-clays, shows that in pre-Chalky Boulder- clay time, not only were the main valley lines marked out, but many even of the smaller valleys, such as the Brent, were in existence. Of course, during Pleistocene time, denudation has been very active ; for over large portions of this area the boulder-clays, gravels, and sands now only occur as scattered patches.
Denudation has been most active in the valleys of the main watercourses, less so in the smaller watercourses, and least in the neighbourhood of ridges and high land. However, even in the main valleys, where the deposits were chiefly gravels and sands, the gravels and sands have protected the softer rocks below them, with the result that the gravels which once occupied the old valley bottoms now cap the hills and higher lands. In many situations the most elevated masses of boulder-clay rest directly upon the older rocks, whereas in lower positions the boulder-clays, especially the Chalky Boulder-clay, generally rest upon sands and gravels. We have here an indication that these sheets of gravel were laid down as extensive fluvio-glacial deposits, their heights above the sea depending upon the slope of the land and supply of material coming from the margin of the ice; or, in the case of valleys up which the ice was advancing and blocking the natural exits, upon the heights of the cols at their ends.
It must be remembered that both during the advance and the retreat of the ice-sheets vast volumes of water were thrown off at their fronts. When we consider that the ice which entered the Thames Valley came from the Scandinavian Peninsula, and that the greater portion of the precipitation on the ice-sheet which occurred between England and Scandinavia was liberated as water near the ice fronts, it is clear that an enormous volume of water was given off at the ice-sheet margins. Such melting took place both during advances and retreats of the ice. During the advances some of the precipitation was stored up as ice, and during the retreats some of the ice was melted, and increased the volume of water thrown off ; but when we consider the slow nature of the advances and retreats, and the great length of time the ice-sheets persisted, it is clear that, as far as flood-water from the ice is concerned, periods of retreat did not differ greatly from periods of advance.
In the Thames Basin, with the exception perhaps of the estuarine portion, the whole district has been above the sea-level ever since the deposition of the Lenham Beds; consequently subaerial denudation had been active over the district for long ages before the Glacial Period, and there must have been an old river system in existence before the advent of the ice. However, as the directions of the main valleys in the unglaciated areas have always been largely as at present, in spite of the increasing development of subsequent streams,
58 R. M. Deeley—-The Thames Valley Gravels.
the old river gravels have been largely destroyed as the rivers cut vertically and horizontally into the land.
For many reasons, in the process of excavating their valleys, rivers at various times bring their valley bottoms to base-level. ‘hey then cease to deepen them, but continue to attack the valley sides, and in course of time lay down extensive sheets of gravel. When a pause in vertical excavation persists for a long period, the surrounding high lands, when the rocks are soft, are denuded until we have a country of low relief through which the rivers course sluggishly over wide plains of gravel and of brickearth formed by floods.
The gravel deposits of the River Thames show that such pauses in vertical erosion occurred several times, for we have the remnants of several of these gravel plains at various heights, some of them forming terraces along the main river valléys, and others far removed from the present watercourses. However, whilst the rivers were excavating their valleys from one base-level to another, they also formed gravel deposits at intermediate heights. It thus comes about that there are gravel patches at almost all heights above the rivers, but there are masses concentrated at particular levels.
During the Pleistocene Period the ice-sheets reached the Thames Basin, and threw into the Thames Valley large quantities of gravel and sand. At these times gravel beds of exceptional thickness and of large area were formed. An endeavour will be made to connect these fluvio-glacial deposits with those of the fluvio-glacial fans near the old ice margins.
The suggestion that the pre-Chalky Boulder-clay Thames Valley, especially the eastern portion, was deeply excavated and subsequently partially filled up with fluvio-glacial gravel has already been made by T. I. Pocock.?
Bearing in mind the considerations outlined above, by the aid of the excellent Drift maps and memoirs published by the Geological Survey, it is possible to make a preliminary outline sketch of the conditions obtaining in the Thames Valley during the Chalky Boulder-clay stage.
To accomplish this object we must proceed from the known to the unknown. In the lower Thames Valley a good deal is known concerning the nature and distribution of the deposits left by the ice-sheet. The unknown is the actual physical condition of the valley in Glacial times; but here we can bring to our aid a knowledge of the nature of the deposits which are being formed by existing ice-sheets and glaciers in such regions as Alaska and Greenland.
The most profitable course to adopt in studying such an area as that of the Thames Valley is to obtain, if possible, a knowledge of the deposits formed at some particular stage, and use these as a datum with which to compare older or newer deposits. .
When the ice which formed the Chalky Boulder-clay reached the north-eastern watershed of the Thames Valley it discharged into the Thames Basin great volumes of water and large quantities of gravel and sand. The deposits formed in this way contain numbers of rocks foreign to the Thames watershed. During such a time we had
1 Geol. Surv. Summary of Progress, 1902, p. 201.
R. M, Deeley del.
Wat fans.
end. Southchurch,
South
Valley.”
Grou. Maa., 1916.
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R. M, Deeley del. Fug. F
IN) Figher Terrace Gravet. Tilehurst Terrace Gravel. == Ice Margin. Flutie Clme deans
3 x ; TSN) Ye ai S oS — sy ay x} S00 Ft x oe sits x < t i 8 : ~~ 3 } RD BER Ts. S88 ; S 3 3s S SSE k S| i > ya S3 GO 5 MESON TIES 3a Ph = Rave =] = pSX Y aS eS s-8 8 38 Sees i oc Y3s $ SNe 300 S fo Se g Re ~~ re == | _ aS aog ae I —-s4_8 100 —_— O
7.9. ca 30 20 7) o Fg. 2. To illustrate Mr. R, M. Degnpy’s Paper on ‘‘ The Fluvio-Glacial Gravels of the Thames Valley.”
4y J ‘ Mc atitetea Sait toe, all BAT: ‘ t ee F Pal i) =f a ‘\ Py , , : 1 V4 : r fe’. fi . ; d Piet - , wry i ") WR a, , Air eke 4 « / 4 - - i. rs . an BI y 5 yw) ¥ eae : e "i i: . ‘tii 7 5 r he ra ° aie Syiy t ‘ fogs te ie , Sete ers et f',
R. M. Deeley—The Thames Valley Gravels. 59
a main valley in which the gravels were deposited over a wide belt, and other tributary watercourses flowing from the ice margin and forming fluvio-glacial fans of gravel and sand. A map showing the probable position of the ice margin, the fluvio-glacial gravel and sand beds in the tributary watercourses, and the area occupied by the fluvio-glacial deposits of the main stream, would furnish such a datum as we require.
If the conditions suggested above ever existed in the Thames Valley, then some of the gravel and sand deposits which exist on the hill-tops and valley sides of the Thames may have formed portions of the fluvio-glacial deposits.
The Map, Fig. 1, has been constructed to show what were probably the conditions obtaining when the ice which formed the Chalky Boulder-clay reached its maximum extension.
A considerable portion of the northern area of the map (Pl. IV, Fig. 1) is occupied by the ice-sheet of the Chalky Boulder-clay. From the various lobes, A to H, powerful streams of water escaped _ down the valleys of the Chelmer, Thame, Colne, Brent, Lea, Roding, and Crouch. These streams formed extensive fluvio-glacial fans, and threw large quantities of water-worn rock debris into the old Thames Valley. ‘I'he probable area occupied by the gravels thus laid down is indicated by the coarse hatching. As the remnants of this deposit now occupy hill tops or shelves on the valley sides and are well developed on the hill on which Tilehurst stands, they have been called the Tilehurst Terrace Gravels. Some gravels, which are probably fluvio-glacial deposits of somewhat greater age, and lie at a higher level, are mapped as Higher Terrace Gravel. When the _ boundaries of the deposits are somewhat uncertain the lines have been dotted in. The dotted line, which runs along the Thames Valley from east to west, and is marked with a scale of miles, is the line of section along which Fig. 2 is drawn.
The ice margin has been drawn so as to include the most southerly patches of boulder-clay known. They probably do show the actual limits of the true glacier flow, but some of the lobes may have projected further down the valleys. West of Luton the ice rested near the edge of the Thames watershed. East of Luton the ice crossed the watershed and was arrested by high land in the Thames Basin. Indeed, the outliers of Chalky Boulder-clay show that the margin of the ice-sheet was determined largely by the topography.
Here and there lobes of ice pressed through the gaps in the hills. Working from west to east the main ice lobes are as follows :—
A. Buckingham Lobe. South of Buckingham there is a gap in the watershed between the Ouse and the Ray in which boulder-clays, gravels, and sands are largely developed. ‘This seems to have been an important line of overflow; for from Stony Stratford past Buckingham to Charndon the overflow valley is well marked.
B. Leighton Buzzard Lobe. Here the ice stream curved round the hill to the south of Woburn and travelled as far at least as Leighton Buzzard.
C. Dunstable Lobe. At Dunstable there is a gap between the Chilterns and the high ground to the north-west, through which ice
60 R. M. Deeley—The Thames Valley Gravels.
passed. Whether the Leighton Buzzard and Dunstable lobes ever coalesced and passed down the valley towards Aylesbury is uncertain. If they did they may have sent floods down some of the gaps in the Chilterns as well as down the Thame Valley.
D. St. Albans Lobe. South of St. Albans there is a large patch of boulder-clay which shows that the ice passed through the gap between Hatfield and St. Albans. The gap has a height of about 250 feet. From the ice which passed through it a great amount of debris was thrown into the Thames Valley down the Colne River, in the valley of which there are wide spreads of gravel, some of the terraces of which are portions of the fluvio-glacial fan formed by the water liberated from the front of the Chalky Boulder-clay ice-sheet.
EK. Brent Lobe. The gravels of Dollis Hill and Hendon show that an ice-flow from the north-east passed through a gap north of Hampstead and Highgate into the Brent Valley. -
F. Lea Valley Lobe. The main ice invasion of the district covered by the Map, Fig. 1, came down the Lea and Roding Valleys and pushed its front into the then forming fluvio-glacial gravels of the Thames; for at Hornchurch the boulder-clay of this lobe has been found resting below the gravel. It must be remembered that the gravels we are considering and the Chalky Boulder-clay are con- temporaneous deposits.
G. Crouch Valley Lobe. A considerable volume of ice mounted the watershed between the Chelmer and the Crouch. Some patches of sand and gravel in the Crouch Valley render it somewhat likely that this valley was occupied by a fluvio-glacial fan which ran in an easterly direction to the Thames Valley.
H. Malden Lobe. A lobe of ice passed towards the east, south of Tiptree Heath, and sent out a fluvio-glacial fan towards the north-east.
Other ice lobes moved towards the east down the valleys of the Suffolk rivers, but how far north the Thames then ran before reaching the sea is unknown at present.
The arrows over the northern portion of the map show the probable direction of the ice-flow. Harmer’ has already given the probable directions of the flow of the ice from the north over the Fenland as far south as Royston. The directions of the ice-flow of the area we are dealing with, as shown on the Map, Fig. 1, are in entire agree- ment with his views concerning the movement of the more northerly portions of the ice. The coarsely hatched area, the greater portion of which follows the course of the Thames River, is the probable area occupied by the Tilehurst fluvio-glacial gravels of the main river when the ice reached its most southerly limits. Along the valley a dotted line has been drawn, and Fig. 2 is a section along this line. The present upper surface of the Thames alluvium is shown by the line AA. The slope amounts to about 2°5 feet per mile.
The terraces and patches of gravel we have to make use of to ascertain the levels and thicknesses of the fluvio-glacial gravels of the old Thames River are not very numerous, and are no doubt mere
1 Jubilee Volume of the Geologists’ Association, vol. i, p. 108.
R. M. Deeley—The Thames Valley Gravels. 61
fragments of the old deposit. Since these gravels were laid down the Thames has greatly deepened and widened its valley, and in doing so has destroyed the larger portion of the old deposits.
When first the water thrown off by the ice passed over the cols and entered the Thames Valley, it may have been muddy; but was free from gravel and sand, these latter being deposited in the valleys up which the ice was advancing, and were subsequently covered up by or converted into boulder-clay. The large volume of water thrown into the Thames Valley would first result in increased erosion and the destruction of much of the old Thames gravel of pre-Chalky Boulder- clay age. However, when the ice reached the watershed, then immense quantities of gravel and sand would be thrown into the valley, and the stream being unable to carry it away the gravel and sand would collect in the valley bottom and form a thick bed. When a river is thus aggrading its valley it does not form one wide stream, but breaks up into a form known as a “‘ braided stream”’.
The Thames Valley may be divided into an upper or Oxford Basin above the Goring Gap, and a lower or London Basin below the Goring Gap, the Chiltern Hills and the high ridge to the south-west separating them. }
When the ice margin stood on the north-east watershed of the upper basin, gravels were formed at heights of 100 feet or more above the present level of the Thames. However, in the Oxford Basin very cold climatic conditions existed even outside the Chalky Boulder- clay ice margin, and there is a marked absence of stratification in the Plateau Gravels of the region. Even if the ice did not override the watershed at one time, it is probable that heavy snow-drifts collected _on the valley sides in sheltered positions, destroying older gravel terraces and disturbing gravels then forming.
In the Geological Survey Memoir for Oxford it is stated that the stones in the high-level gravels are a very mixed collection; among _ them occur numerous partially rounded flints a few inches across, liver-coloured quartzites doubtless from the Bunter Pebble Beds of the Midland Counties, white vein quartz, various coloured quartzites, hard sandstones resembling greywethers, soft sandstones with felspar of the Millstone Grit type, and black lydian-stone. The highest outlier on the Oxford sheet is at Bower’s Hill, 540 feet O.D., but this deposit is doubtless much older than the Chalky Boulder-clay.
In the Oxford Basin the Plateau or Fluvio-glacial Gravels are not well developed, having suffered very considerably from the erosive action of the rivers and streams, and perhaps from the collection and movement of snow masses. However, there are some outliers of gravel, etc., at levels of 300 feet above O.D., which would appear to belong to the series formed whenthe Chalky Boulder-clay ice stood on
the watershed to the north-east. The patches between Ipsden and _ Lewknor, extending along the edge of the Chilterns at heights of 300 to 400 feet above O.D., may be partly of this age; but as they are almost wholly flint gravels formed of materials derived from the weathering of the Chiltern Hills, they may be of various ages.
In the basin of the Thames at.Chiselhampton and Great Milton, there are patches of gravel at heights of about 290 feet above O.D.
62 hk. M. Deeley—The Thames Valley Gravels.
which may be connected with fluvio-glacial fans which came from the Leighton Buzzard and Dunstable Lobes, for they both contain pebbles of the Northern Drift. Patches of gravel at about the same height also occur in the neighbourhood of Oxford, ete. The drift deposits in the north-western portion of the Map, Fig. 1, have not been surveyed in detail, but enough is known to show that large fans of fluvio-glacial gravel from the Buckingham Lobe occur there. Owing to the fragmentary nature of the drift deposits in the Oxford Basin, and the fact that some areas have not been mapped in detail, the probable distribution of the fluvio-glacial deposits of this district have been drawn in dotted lines. The evidence furnished by these much disturbed and denuded high-level gravels is to the effect that when the Chalky Boulder-clay ice poured its debris into the Oxford Basin of the Thames Valley, portions of the basin had been denuded so as to form an extensive flat area which now stands about 300 feet above the sea. Over this area the fluvio-glacial gravels were spread in a great sheet covering such of the old river gravels as remained, and also the surrounding low country. The floor upon which the gravel rests is now wonderfully level, the slope towards the outlet of the Oxford Basin at Goring being quite small. The 300 feet fluvio-glacial gravels of the Oxford Basin may have been fifty feet thick, as they are further down the river; but mere fragments of them remain.
When a terrace is spoken of as being the 300 foot terrace it must be understood that the gravel and sand rest upon a platform of older rocks whose upper surface is at a height of 300 feet above O.D.
During the Chalky Boulder-clay period there must have been a very large stream of water flowing through the Goring Gap, a stream which partially dried up in the winter months. With this stream came Bunter pebbles into the London Basin, thus accounting for their presence to the west of points where they also reached the area from the St. Albans Ice Lobe.
On Fig. 2 the heights above the sea and thicknesses of a number of these outliers of gravel inthe London Basin are plotted. The fluvio- glacial and other old gravels of this area, although the district has suffered much denudation, are less fragmentary in character than in the Oxford Basin. Indeed, they cover very considerable areas and their arrangement is much more easily traced.
In Fig. 2 the dotted line BB shows the average height of the bed upon which the ‘schotter’ formed by the ‘ braided streams’ rested, whilst the line C C shows its upper limit. These levels must only be regarded as approximately correct. The gravel beds must have varied very considerably in thickness, often finishing off as a feather edge on the slopes of the valley sides. The gravel and sand patches which have been used to draw these lines are shown on the section, being named after some small town, village, or hill. The heights have been ascertained as closely as possible either from Ordnance Survey contoured maps or from the Drift coloured maps of the Geological Survey.
In the Thames Valley, east of Goring, and generally capping the higher Tertiary hills, there are deposits which Whitaker has called
R. M. Deeley—The Thames Valley Gravels. 63
the Pebble Gravel. The pebbles are well water-worn, and consist of flint, quartz, and quartzite. They are certainly much older than the Chalky Boulder-clay, as can be seen from the relationship of the two deposits near Potters Bar and the region immediately to the north- east. On Fig. 2 the dotted line D D shows the general slope of these Pebble Gravels to be about 4:4 feet per mile as we goeast. However, the direction of the section is not quite along their dip slope. At one time the Pebble Gravels must have been a wide-spread deposit, but whether they are the remnants of the gravels of an old river and its tributary streams is uncertain. It is owing to the protection the gravels afforded to the soft rocks below that the deposit now occupies high ground above the softer surrounding rocks.
At much lower levels, and sloping in somewhat the same direction as the Pebble Gravel, we have what are here considered to be the fluvio-glacial gravels and sands of the Chalky Boulder-clay ice-sheet.
They stand at heights which lie roughly, as previously stated, between the levels shown by the dotted lines B B and CC, Fig. 2.
In Fig. 1 the coarsely hatched area of the Tilehurst Gravels shows the ground which was probably occupied by the fluvio-glacial gravel of the Chalky Boulder-clay period. It is suggested that the bottom of the valley was then flat, denudation having reduced the level of much of the surrounding soft rocks to base-level, the whole area, where it was sufficiently low, being covered by a thick sheet of gravel. There may have been numerous ridges, low hills, and gravel terraces standing above the plain which were not covered by gravel, consequently the whole of the hatched area may not have been covered by the deposit.
In the neighbourhood of Goring the base of the gravel stands at ~ about 3800 feet O.D. Up the Kennet Valley it is a little higher, whilst it falls rapidly in an easterly direction. On this account it is not convenient to call the deposits the 300 foot terrace, and they will be referred to as the Tilehurst ‘errace Gravels for distinctness.
At about ninety-four miles from the margin of the map, Fig. 1, there is a deposit of gravel and sand on the hill to the west of Tilehurst. Its highest point and the level of the rock terrace on which it rests are indicated by the vertical line. Monckton! describes this deposit, and some of the other gravels to be referred to, as glacial gravels, and states that they contain quartzites, large blocks of quartz, and igneous rock. By the Geological Survey they are described as being as a whole ‘‘distinctly current-bedded, though this character is more conspicuous in some pits than in others”’.
In the Kennet Valley on the ridge to the north-east of Beenham, at nearly 100 miles, there is gravel and sand at about the same level as at Tilehurst. Other high-level gravels at Sonning, Finchampstead, Hurley, Bisham, and Winter Hill belong to this terrace.
From Flackwell Heath to Harefield the deposits plotted are those of the St. Albans Ice Lobe, glacio-fluvial fan gravels and sands. In
1 Q.J.G.S8., vol. xlix, p. 309, 1893. 2 The Geology of the Country around Windsor and Chertsey (Mem. Geol. Surv.), p. 60.
64 - René Fowrtau—The Eocene of Egypt.
the Colne Valley, 3 miles south of St. Albans, is a patch of Chalky Boulder-clay resting upon sand and gravel. The gravel comes down to a level of about 230 feet, and the Boulder-clay les between the levels 250 and 290 feet or thereabouts, whilst the same deposit of gravel is from 310 to 335 feet high on the other side of the river to the south-east. The presence of a patch of Boulder-clay up the Colne River, 12 or 14 miles from the Tilehurst Terrace Gravels, and almost as low down as the section line BB, Fig. 2, is remarkable. However, the fluvio-glacial gravels near the Boulder-clay patch rise as high in places as the section line C C where it passes the confluence of the Colne River and the Thames.
It would appear that the Chalky Boulder-clay ice built up in front of it a mass of gravel and sand whose upper surface was considerably above the lower level of the ice and boulder-clay. When this takes place and the glacier is retreating, large masses of glacier ice are left beneath the gravel plain, and these melting out form great pits in the alluvial deposits. Such a condition of affairs may now be seen in the valley of Hidden Glacier,’ Alaska.
(To be concluded in our next number.)
TV.—Tue Divisions or tHe EKocenr or Eoypr AS DETERMINED BY THE SuccEssion oF THE Ecutnip Faunas.
By RENE Fourtavu, Member of the Egyptian Institute, etc.
VERY remarkable fact in the paleontological study of the
Eocene strata of Egypt is the succession of echinid faunas, which seem definitely localized at well-determined horizons, enabling these to be recognized with ease.
The opening of the Eocene period is marked by the appearance of a group consisting of Conoclypeus Delanouei, de Loriol, Plesio- spatangus Cotteaut, de Loriol, Linthia cavernosa, de Loriol. C. Delanouet characterizes the strata to which the Egyptian geologists have given the name of Libyan. L. cavernosa appears almost at the same time as C. Delanouei, but disappears earlier ; it is no longer met within © the upper beds of the Libyan stage, which are characterized by the abundance of Foraminifera of the genus Alveolina, and in which a new echinid fauna is recognized. Finally, Plesiospatangus Cotteaut occurs only in the central portion of the Libyan stage.
In addition to these three very abundant species, others of less frequent occurrence may be mentioned. Such are Opzsaster thebensis, de Loriol, exclusively restricted to the lower part of the Libyan stage; the group of Megapneustes (IL. Sickenbergerit, Mayer-Kymar, M. Lorioli, Gauthier, If. grandis, Gauthier), and Linthia Delanouet, de Loriol, which are only met with in the central portion.
The upper part of the stage, which has received the special name of the ‘‘ Alveolina Series’’, contains, in addition to C. Delanouet, Lichinopsis libyca, de Loriol, Eehinolampas Humet, R. Fourtau, Sismondia Logotheti, Fraas, Hypsospatangus Lefebvrer, de Loriol.
C. Delanouei is represented at this horizon by a somewhat peculiar
1 The Yakutat Bay Region, Alaska, by R. 8S. Tarr, p. 63.
René Pourtau—The Hocene of Egypt. 65
variety in which the periproct is unusually developed, tending to be nearly as broad as it is long, and penetrating the posterior border; E. Humet, very rare below, abounds in certain localities ; S. Logothett is restricted to the ‘ Alveolina Series’’, but only in the south; to the north it is replaced by S. varians, R. Fourtau, which is also limited to this horizon. Z. libyca and H. Lefebvrei are among the most characteristic forms and are present almost every where.
In addition, the ‘‘ Alveolina Series”? yields a number of forms which are only prevented by their very narrow localization from being characteristic: such are Levocidaris miniehensis, Mayer- Kymar; the genus Gisopygus (two forms of which appear ata slightly lower horizon), which attains a splendid development in the ‘‘ Alveolina Series’’, to disappear almost completely with them; ephrenia Lorio, R. Fourtau, Schizaster miniehensis, R. Fourtau, Huspatangus Lamberti, R. Fourtau, and Cheopsia Mortensent, R. Fourtau.
Thick masses of limestones containing enormous numbers of Nummulites gizehensis, Khr., appear above the ‘‘ Alveolina Series ”’ in Egypt. With them, the echinid fauna changes absolutely. The species we have just mentioned disappear, making way for others which have not yet been found in the lower strata. These are: Porocidaris Schmidelui, Minster, Hchinolampas africanus and its variety Mraasz, de Loriol, Schizaster africanus, de Loriol, S. moqatta- mensis, de Loriol, Huspatangus formosus, de Loriol. These forms are met with throughout the mass of limestones with Vummulites gizehensis, accompanied according to locality by less abundant species such as: Levocidaris Abbater, Gauthier, generally distributed, Brisso- _ spatangus Hume, R. Fourtau, in the southern area, Orthechinus mogattamensis, Cotteau, and Brissopsis Lamberti, Gauthier, in the northern portion. Then follow a whole series of limestones in which no echinids have been found. They are characterized by the . abundance of branching Bryozoa and Serpule.
_ The strata above these limestones are almost lacking in Nummulites, but yield a special sea-urchin fauna, including: Rhabdocidaris Gaillardoti, Gauthier, Thagastea Luciani, de Loriol, Eehinolampas Cramert, de Loriol, Anisaster gibberulus, Michelin. To these may be added the following species, which are more rarely met with: Thylechinus libycus, R. Fourtau, Echinolampas moelehensis, R. Fourtau, in the southern area, Sismondia Blanckenhorni, Gauthier, and Clypeaster Fourtau, Lambert (=C. Breunigz, de Loriol, non Laube), in the northern portion.
Above these deposits is a series of marly or calcareous strata without sea-urchins, and in the Fayum mainly containing vertebrate remains.
These successive faunas enable us to establish definite divisions for the Eocene of Egypt.
In the first place, we can define two main divisions of which the line of demarcation is easily traced in consequence of the disappear- ance of Conoclypeus Delanouet and the appearance of Hehinolampas africanus, which inaugurates the group of conoclypeiform Echinolampas, apparently derived from C. Delanouev.
DECADE VI.—VOL. II.—NOo. Il. 5
66 René Fourtau—The Eocene of Egypt.
This demarcation line also corresponds with a notable change of facies and with the appearance in Egypt of the large Nummulites constituting the JV. gizehensis group. ‘These two divisions have been long established and adopted almost unanimously by geologists who have studied the Kocene of Egypt. They are the Libyan and Mogattamian Stages.
The Libyan Stage can be subdivided into—
1. Lower Libyan, where C. Delanouwec is present alone with Linthia cavernosa.
2. Middle Libyan, in which with C. Delanowei and L. cavernosa appear Plestospatangus Cotteaui and the group of Megapneustes, which is only found at this horizon.
3. Upper Libyan, long ago separated under the name of ‘‘Alveolina Series’’, which still contains some C. Delanouet, but none of the other species. These are replaced by small forms, of which the most abundant is Hypsospatangus Lefebvrer.
The Mogattam Stage, which following the rules of nomenclature we should term Moqattamian, can be easily divided into two sub- stages—
4. The Lower Moqattamian is characterized by large conoclypeiform Echinolampas, together with Schizaster africanus and Huspatangus Sormosus.
5. The Upper Moqattamian in which the sea-urchin species of large size are replaced by others that are quite small, such as Thagastea Lucian, Echinolampas Cramert, Anisaster gibberulus, accompanied by Schizaster vicinalis, Agassiz, while in the uppermost layers the genus Clypeaster appears for the first time in Egypt.
The synchronization of the local divisions is somewhat delicate, and has of late given rise to somewhat lively discussion. The Echinids have not been used to establish the divisions adopted in Europe, and latterly efforts have been mainly applied to determining a Nummulite scale, which, it must be admitted, has given good results in many places, but which might give rise to criticism when applied to other localities and especially North Africa. It is not easily to be explained, for instance, why, in Tunis and Algeria, the beds with Mummutlites. gizehensis are attributed by everybody to the Lower Eocene, whereas in Egypt all agree as placing them in the Middle Eocene. The study of the Cercthium group has given fairly good results in the Paris Basin, but division on such a basis is impossible in Egypt, where these Gasteropods are rare, and when present are usually distinct species.
It might be therefore useful to take the succession of echinid faunas and changes of facies as our basis in attempting to subdivide the Eocene of Egypt, and to attach only a relative value to synchronizations founded on widely separated faunas. The Table (p. 67) indicates the solution which appears to me the most satisfactory.
The synchronizations which I propose in this Table appear to me rational. There might, however, be discussion as to the desirability
67
René Fowrtau—The Eocene of Egypt.
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68 A. J. Pickering—Borings for Water
of including the Bartonian and the Ludian in the Middle Eocene, and of only beginning the Upper Eocene with the Tongrian. The stratigraphical divisions adopted in Europe correspond to marked oscillations of shore-lines, and their delimitation is easy. It is not so in the Mediterranean Basin and especially in its southern part, which, during the whole of the Eocene period, was a region of continuous sedimentation. I have thought that the sea-urchin faunas could help us to establish subdivisions, and have given the result of my researches without stopping at simple questions as to where the brackets representing individual divisions should be drawn.
I am greatly indebted to Dr. W. F. Hume, F.G.S., etc., Director of the Geological Survey of Egypt, for kindly translating this paper into English.
V.—On two Bortnes ror Water at Hinckiey, LEICESTERSHIRE. By A. J. PICKERING.
HOUGH Hinckley is now possessed of an excellent supply of water brought from the Lower Keuper Sandstone of Snarestone, in North-West Leicestershire, up to 1891 it had an unenviable reputation for abortive water-schemes. Some £20,000 had been spent in considering eighteen different propositions and in carrying out three deep borings within a few miles of the town. During this time six consulting engineers were called in by the local authority. All these schemes failed, not through any lack of water—for this was obtained from the Waterstones of the Lower Keuper in almost unlimited quantity—but because it was found impossible to shut out the chlorides and sulphates from the gypsiferous Keuper Marls through which the borings passed.
Recently two attempts have been made by private firms in the town to obtain a supply of water from the Upper Keuper Sandstone, but unfortunately these schemes have been abandoned without satis- factory results.
The first was carried out for Messrs. Atkins Bros. at the rear of their factory in Bond Street in the centre of the town. Boring was commenced in July, 1913, from the bottom of an existing well 41 feet deep. This had up to late years yielded an excellent supply from the Drift deposits (here about 135 feet in thickness), but had gradually been drained, probably by the sinking of deep foundations in the lower levels of the town and by extensive building operations in the higher levels. This latter would have the effect of diminishing the quantity of rain-water making its way into. the water-bearing drifts. In this boring the jumping-chisel method. was employed throughout; consequently the thicknesses of the beds were somewhat difficult to ascertain. In the following table they must be taken as only approximate. Operations were abandoned in 1914 after repeated attempts to recover a boring-tool, and through the falling-in of the unlined portion of the borehole.
The following is the section :—
at Hinckley, Leicestershire. 69
WELL AND BORING, BOND STREET, HINCKLEY.
(125 yards south-east of junction of Bond Street with Upper Bond Street and
the Hollycroft.) 4 Thickness. Depth.
Feet. Feet. i Mopysoils : : : : : : : 2 2 2. Chalky boulder- -clay : : : ; . ; . 10 12 3. Sand and loamy sand . : 3 29 41 4, Sand and running sand, light brownish- yellow : 4 11 52 5. Red-brown clay, sandy P : : 5 : : 3 55 6. Grey-brown sand ; , ; ‘ : 3 F 5 60 7. Brown silty clay F : : 10 70 8. Loams and clays, very ‘fine, light- “brown : : : 10 80 9. Brown silty clay (as No. 7) ; : ‘ : : 9 89 10. Reddish-brown silty elBy : : : Be ets : 11 100 11. Dark-brown clay . : ‘ : : : ; 10 110 12. Light-brown clay 18 128 13. Dark-brown oe with pebbles of ironstone and grit and patches of red marl. : : 7 135 14, Light-red marl with green spots and small pebbles” : 25 160 15. Light-green and red marls with thin bands of sandstone 30 190 16. Red marls with green mottling : ; é 8 198 17. Coarse grit . * ‘ 3 : : ¢ 3 201 18. Marls with gypsum . : : : : 22 223 19. Hard grey sandstone, fine- erained 5 : : 2 225 20. Hard red marl . : : 0 : : : 19 244 21. Sandstone (as No. 19). : E : ; : : 5 249 22. Hard sandstone, close-grained . : : : : 7 256 23. Red marl without gypsum . ; : 34 290 24. Red marl with green spots and traces of gypsum . . 10 300 25. Hard red marl . ; : 8 308 26. Harder red marl with conchoidal ‘fracture 2 : . Undetermined.
No. 2 is the typical Chalky Boulder-clay of the Midlands, con- taining here a considerable number of Chalk flints and Jurassic fossils; of these the Gryphea arcuata is the most common. It is _ blue-grey in the higher beds, but assumes a redder colour as it approaches the underlying sands. In and near Hinckley it often becomes gravelly, the clay being replaced by a coarse sandy matrix. This gravel is sometimes matted together by a calcareous cement.
Nos. 3, 4, 5, and 6 are a sandy series of the Drift, and are, or have been, exposed in many sandpits in and around the town. They vary considerably in appearance, some beds being red and loamy, others pale-yellow and of a ‘sharp’ and crystalline nature; in the latter case the sands weather quickly to a loam on exposure. Interstratified with this sandy series are a few bands of very fine gravel, containing derived shell-fragments in beds of not more than an inch or two in thickness. ‘They also contain thin streaks of black carbonaceous material, probably coal-dust. Current-bedding is conspicuous in all the sands, which are entirely devoid of flints, and are mainly derived
1 Six-inch map, Leicestershire 42 N.E.; one-inch New Series map 169 (Nuneaton); one-inch Old Series geological map 63 S.W. Height above O.D. about 410 feet. Rest-level of water about 80 feet from surface. Pumping-test at a depth of 305 feet yielded 1,400 gallons per hour. Old sunk well 41 feet, new borehole 267 feet; total depth 308 feet. Made by Messrs. Peacock & Bird, Hinckley. Commenced July 23, 1913; abandoned January, 1914. Chisel used throughout.
70 _ Aw SJ. Pickering—Borings for Water
from Triassic outcrops. From their position they may be, I think, correlated with the Quartzose Sand of the Lower Pleistocene identified by R. M. Deeley in the Trent Valley. Wherever these sands occur in the neighbourhood of Hinckley they are underlain by thick beds of clay ; consequently they form a natural reservoir and yield a considerable supply of water whenever penetrated below the valley levels. During a recent enlargement of the main sewers in the lowest part of the town these beds of sand were encountered, and the contractors experienced great and unforeseen difficulties in keeping the running sand from their trenches. A large portion of the street subsided as a consequence of the washing away of the underlying sand.
Beds 7 to 12 are a series of clays or brick-earths, which are, or have been, worked in several brickyards north, east, and west of the town, e.g. at Messrs. Hudson’s works, Barwell Lane. They are quite free from erratics, save a few small pebbles of quartzite and felsite.
Nos. 13 and 14 are the lowest beds of the Drift. They contain a considerable proportion of Keuper Marl material, also numerous Bunter pebbles and rolled fragments of Coal-measure sandstone.
Nos. 15 and 16 appear to be Upper Keuper Marls with bands of coarse sandstone or skerry.
Nos. 17 to 22 contain a succession of fairly massive beds of Upper Keuper Sandstone of varying degrees of hardness, with an inter- vening 22 ft. bed of mottled marl witha little gypsum.
Nos. 28 to 26 belong to the thick lower series of Keuper Marls containing the usual bands of gypsum.
The second boring was begun for Messrs. A. EK. Hawley & Co., at their Sketchley Dye Works, early in 1915. After boring 213 feet without any satisfactory results the work was abandoned (for the present) in August last. Unfortunately the first 110 feet were bored by the percussion process, so that again it was impossible to ascertain the thickness of the Glacial Drift with any degree of accuracy. From 110 to 213 feet the engineers used the shot-drill, extracting cores of about 7 inches in diameter.
The following is the section :—
WELL-BORING, SKETCHLEY DyE WoRKS, HINCKLEY.! (330 yards S. 7° W. of railway-bridge over Rugby Road.)
Thickness. Depth. ft. in. ft. in, 1. Top soil, sand and gravel : : : : 2 0 2 0 2. Red clay P : : : 3 : : 8 0 10 0 3. Brown silty clay . : SO. 0 50 0 4. Brown silty clay intermixed with red marly clay 5. Brown silty clay with fragments of red marl,
small pebbles of quartzite, and pieces of ~
green sandstone 2 0 15 0 6. Red marl with quartzite pebbles (pebbles larger
towards base)
1 Six-inch map, Leicestershire 42 BE. one-inch New Series map 169 (Nuneaton); one-inch Old Series geological map 63 S.W. Height above O.D. about 327 feet. Engineer, Mr. Chas. J. Ell, Luton, Beds. Commenced February, 1915; work suspended following August.
. Red marl with a little green marl . Hard red marl :
. Green marl
. Red marl 3 : : : ;
. Red marl with three 2 in. bands of gypsum . Red marl ‘
. Mottled (red and green) m marl with little By psum . Gréen marl
. Red marl
. Gypsum
. Red marl
. Green marl
. Red marl
. Gypsum
. Red marl
. Mottled marl with eypsum veins
. Red marl, calcareous ?
. Mottled marl with gypsum veins
. Green marl .
. Mottled marl, chiefly red
. Gypsum
. Mottled marl, ‘chiefly red : F . Green and red mar! with sypsum contorted
at Hinckley, Levcestershire.
bedding-lines
. Gypsum x 9 . Green and red marl ; horizontal bedding . Red marl with three bands of eypsum
. Red marl
- Red marl with veins of gypsum
. Green marl é
- Gypsum
. Red marl
. Red marl with thin veins of sypsum
. Red and green marl ;
. Gypsum :
. Red marl
. Gypsum
. Red marl, slightly mottled . Gypsum
. Red marl
. Gypsum
. Red marl, slightly mottled . Red marl with veins of gypsum - Red marl ; F ‘ : . Gypsum
. Red marl
. Green marl .
. Red mar! with a little gypsum
. Green marl .
. Red marl with veins of gypsum . Red marl ; : . Gypsum
. Red marl
. Gypsum
. Green marl
. Red marl
POOR OWNONOROFPNHFONONONODORNOOCOHUWRHROF
a FPONOCOHOWFHOHREDRONONANODOW
: Thickness, . Clear red marl “ y : : 5 : iyi. . Red and green marls. 21 0 - Red marls with small quantity of gypsum . Hard red marl ‘|
ooooconaq SCWWRADWEHEWAROHONOCOCORDS ©&
bh
Nj
194 198 198 201 201 204 207 207 211 211 211 213
i)
e DNOONHEHWOrFANADNINCOOCORAS
fe — SWwWoPPWONTRE RE RwWodantoe
WoaRWwWHDoODDaHH whip CW WS
72 A, J. Pickering—Borings at Hinckley.
It will be noticed that this boring commenced at the bottom of the sandy Drift series. The site being 83 feet below Messrs. Atkins’s boring, the Chalky Boulder-clay was not present.
Beds 2 and 3 are the silty clays, and Beds 4, 5, and 6 are the Keuper Drift beds before mentioned. Below these the compact red marls of the Keuper were penetrated, and these continued with interbedded green marls and gypsum as far as the boring was carried.
With the exception of indications of contemporaneous puckering in Bed 33 the whole of the cores were horizontally bedded.
The absence of all trace of the Upper Keuper Sandstone (either in the sediment of the earlier portion of the boring, or in the cores) is a little remarkable, inasmuch as the site is little more than three- quarters of a mile from the boring at Messrs. Atkins Bros., where beds up to 7 feet in thickness were penetrated. The Holy Well boring,’ begun in 1875 a little farther east, also gave about 30 feet of Upper Keuper Sandstones; but at the Wharf boring,’ 1} miles west of the Holy Well and half a mile west of the Sketchley Dye Works, only 12 feet were present.
This absence of the Upper Keuper Sandstone in the Sketchley borehole may be due to one of several causes. Firstly, this sandstone is known to be impersistent at its outcrop in many parts of the Midlands, and is liable in places to thin out, and elsewhere to be split up by beds of marl. There is evidence, too, that more than one band comes in at about this position in the Keuper Marl. Sometimes several bands may be present together in one district, while a little farther on one or other of these bands may thin out. Secondly, although present at the Holy Well and at Bond Street, it may have cropped out against the base of the Glacial deposits before reaching Sketchley. Thirdly, there may be a gentle syncline under Sketchley, by which the sandstone is carried down below the bottom of that boring. This third explanation is supported by the fact that between the Holy Well and Bond Street the base of the sandstone falls 88 feet. If this fall is maintained it would carry the bed below the bottom of the Sketchley boring.
It is to be noted that at the Holy Well the distance between the top of the Waterstones (= Lower Keuper Sandstone) and the bottom of the Upper Keuper Sandstone is 217 feet, whereas at the Wharf the distance is 396 feet. It is probable, therefore, that the Upper Keuper Sandstone of the Holy Well thins out or splits up before reaching the Wharf, and that the Upper Keuper Sandstone at the Wharf, 12 feet thick, is a higher band.
An examination of the cores showed both the red and the green marls to be entirely devoid of organic remains. The green marls were throughout much harder and coarser-grained than the red, and portions were slightly calcareous. The red marls quickly decomposed on exposure; but the green marls showed little signs of weathering. The usual bands of skerry were entirely absent.
The writer is indebted to Messrs. Atkins Bros. and to Messrs. A. E. Hawley & Co. for permission to watch the boring operations, to
1 Rep. Brit. Assoc. for 1875, p. 136; for 1879, p. 160. 2 Ibid. for 1882, p. 226; for 1883, p. 154; for 1887, p. 364.
W. D. Lang —Calciwm Carbonate and Evolution. 73
measure and describe the materials brought up, and to put the results on record. This work has been facilitated in every way by the boring firms engaged.
For several suggestions and general encouragement the writer is indebted to Mr. T. C. Cantrill, of the Geological Survey.
ViI.—Caucruom Carponare AND Evoturion 1n Ponyzoa.! By W. D. Lane, M.A., F.G.S.
te a review in the Grotogicat Magazine for 1913? of an important paper by Cumings on the development and systematic position of the Monticuliporoids, it was pointed out that the elucidation of the post-embryonic stages of that group conclusively proved them to be Polyzoa, and disposed of Kirkpatrick’s contention that they were allied to Merlia, a recent siliceous sponge. Thus, further to prove the dissimilarity between the Monticuliporoids and IMerlia is to flog a dead horse. Nevertheless we welcome the excellent figures by Cumings and Galloway of the microscopic structure of the two organisms showing that the skeleton of the one is formed of super- posed layers and the other of radiate spicules so adjusted as to form a mesh-work.
The authors, however, are not mainly concerned with the connection of Merlia and the Monticuliporoids, but with the Trepostome wall and various correlated structures, namely Cysts and Cystiphragms, Intrazocecial spines, Acanthopores and Communication-pores. They point out that Communication-pores of Paleozoic Trepostomata resemble those of Heteropora—a form that persists until recent times ;_ ‘that Acanthopores are the continuations below the general zoarial surface of hollow spines, ‘‘ undoubtedly protective’? in function, which, in unworn specimens, project above the surface ; that ‘‘ certain extraordinary spines projecting into the submature region of zocecia “of a species of Nicholsonella’’ resemble those of Heteropora neozelaniea, as figured by Nicholson. They make the very interesting and ingenious suggestion that Cysts and Cystiphragms are the expression of the renewal of the polypide on the formation of a Brown Body (a familiar process among recent Polyzoa) and that the purpose of the ectocyst in laying down a fresh wall at each such crisis is the ‘restriction of intrazocecial space’’; moreover, the occurrence of minute concretions of some iron compound in the Cyst, i.e. the space enclosed by the cystiphragms, is claimed to be produced by the decay of the degenerated polypide.
Finally, the structure of the wall is considered. Hitherto it has been customary to divide the Trepostomata by their walls into two groups—lIntegrata, those that have a dark median line in the wall in virtue of which each half is claimed for that zocecium adjoining it— and Amalgamata, in which there is no dark line, but the walls of two
1 [Originally written as a review on ‘‘ Studies of the Morphology and Histology of the Trepostomata or Monticuliporoids’’, by E. R. Cumings and J. J. Galloway, 1915, Bull. Geol. Soc. America, Vol. xxvi, pp. 349-374, Pls. 10-15, but considered more appropriate as an original paper.—ED. |
2 GEOL. MAG., Dec. V, Vol. X, pp. 32-36.
74 W. D. Lang—Caleiwm Carbonate
adjacent zocecia are completely confluent. Cumings and Galloway show that this distinction does not hold—that Lee had already remarked that the presence or absence of the dark line was inconstant —and their researches correlate the presence of the dark line with the thinness of the growing edge of the wall and the consequent ‘‘ steep pitch” of the growth-lamine. ‘‘ For some reason, wherever the wall lamine of the trepostomes are sharply bent the material appears dark ... It is probable that the size and arrangement of the minute granules of which the wall laminz are composed differ slightly at such points from the normal size and arrangement in other parts of the wall. In fact, in well-preserved material and in very thin sections it can be shown that this is actually the case.”
The similarity of the Trepostome wall with that of the Brachiopoda when they are viewed in thin sections is pointed out, and ‘‘in such sections as are shown in figures 45 and 49 it amounts almost to identity’.
Perhaps the most interesting part of the paper concerns the Cingulum or secondary thickening of the wall, and its relation to the secretion of diaphragms and cystiphragms which are clearly shown in the figures to be continuations of this secondary thickening. The authors regard the thickening as an old-age character. ‘‘ The thickening of the interzocecial walls, due to the development of the cingulum, is often very great—far greater than would merely com- pensate for the increasing separation of the zocecia, as they extend radially outward from the axial region. There is an actual reduction
\in size of the zocecial chamber; indeed, in some cases, an extreme reduction (figures 1 and 17). We believe that this extreme develop- ment of secondary deposits is a senile feature, analogous to the great thickening of brachiopod shells and the shells of the Mollusca in old age. In recent Bryozoa the zocecia of the older portions of zoaria often become almost or quite filled up with stony deposits, and it seems that the ectosare [ectocyst] may continue to secrete such deposits after the polypide has wholly disappeared from the zocecium.”’
Let us go further. Say that some metabolic process, such as one involved in nitrogenous excretion, resulted in the precipitation of calcium carbonate in the tissues or upon the surface of a marine organism—Mollusc, Brachiopod, or Polyzoan, and was turned to useful account as affording a supporting or protecting skeleton or shell; that this production of calcium carbonate became increasingly constitutional so that the mere need for a skeleton or shell was more than met; that the process could not be arrested or countered in all the organisms that had acquired it, and in these the disposal of superfluous calcium carbonate became a pressing problem; that, finally, those organisms that found no way out of the difficulty were doomed to extinction under a mass of calcium carbonate of their own making.
At some time or other most animal phyla have met the calcium | carbonate problem in an acute form. The Protozoa can always crawl away from their skeleton, and many organisms that build tubular shells can similarly move up their tubes which thus become of indefinite length, while tabule, diaphragms, etc., are merely the
and Evolution wn Polyzoa. 75
superfluous calcium carbonate of the organism’s after end in its new position. Even Gasteropod Molluscs to a certain extent can behave in this manner. The Arthropods wrestle chiefly with chitin and throw off its accumulation at each ecdysis; but such marine forms as add calcium salts to chitin tend to be cumbered more and more with their exoskeleton at the periodic moults in proportion to the amount of calcium present. Some Molluses, like the Rudiste, have succumbed to masses of calcium carbonate, but the most successful, apparently, have learnt how to circumvent its secretion and produce little or no shell. The point need not be laboured, but this aspect of the deposition of calcareous skeletal matter may help to explain much that is not otherwise clear in the structure and evolution of Polyzoa.
The simplest Polyzoa—the less differentiated Cyclostomes—have tubular skeletons, and merely add to the length of their tube, occasionally inserting a diaphragm, and an entombing cap or ‘closure’ may be the moribund act of a senile individual. As the colonies become more massive it is required that the general zoarial surface should remain at the same level, and this could not be attained if each individual independently moved up its tube according to its capacity for calcium carbonate secretion. The forward movement would, therefore, be general and slow, and the deposit of calcium carbonate would be chiefly directed to the interzoccial spaces which generally would tend to widen as the tubular skeletons radiated from a common centre. This is the condition of the more complicated Cyclostomes and the Trepostomes and Cryptostomes in general. But, though the uneven projection of individuals from the surface of the colony is undesirable, skeletal projections that did not interfere with the currents and food supply would not only be harmless, but might even serve a protective purpose. Thus, when the pressure again became intolerable, acanthopores might arise. Again, if the insistence of calcium carbonate was severe, the whole of the ectocyst capable of, yet not actually, secreting would be in a state of unstable equilibrium, an external stimulus might start the deposition of calcium carbonate at any point, and an intrazoccial spine result. Cumings and Davenport do not suggest a utilitarian origin for these. ‘* What possible functions these spines could have we do not venture to say.”” The renewal of the polypide may well have given the necessary stimulus for the formation of cystiphragms and been the excuse for depositing calcium carbonate even if there were no other need for it. Finally, it is unnecessary to look for any special utility in the massive secondary wall-thickening termed by the authors the cingulum, if the whole organism is (so to speak) aching to deposit it. Cumings and Davenport attribute the secondary thickness of the walls to senility of the individual, at least they say it accompanies senility. We claim, further, that it marks the senility of the lineage to which the individual belongs, and it is by turning to harmless or possibly useful account the same ever-present danger that other structures described in this paper are due.
Such a conclusion has been impressed upon the writer by the study of Cretaceous Cheilostomes. The Cyclostomes and Trepostomes have been considered. The Cryptostomes divert their excess of calcium
76 W. D. Lang—Caleiwm Carbonate and Evolution.
carbonate into the elaboration of secondary apertures. The Cheilo- stomes do the same with marked (temporary) success. But this is only one of their methods. The most hopeful of the Cheilostomes are those which have a skeleton of chitin only. When once calcium carbonate has begun to be deposited the whole lineage is doomed to a more or less stereotyped sequence of calcification until, in the end, it becomes extinguished under its superfluity of skeleton. For obvious reasons it is only these doomed lineages that we have to deal with as fossils; and the evolution of the Cretaceous Cheilostomes, as far as we can have any knowledge of it, is the story of the progressive elaboration of the calcareous skeleton until this becomes secondarily simple by the blotting out of its complexity under secondary deposits.
The simplest Cretaceous Cheilostomes—‘ Membranimorphs ’—have calcareous skeletons with no intraterminal front walls.’ Senility in an individual results in the complete calcification of the intraterminal front wall and the consequent death of the zooid, since even the orifice is sealed up. Before this takes place, however, superfluous calcium carbonate, in some forms, is deposited as terminal spines.’ The general phylogenetic future of some of these, namely those in which the terminal spines, arching over, fuse with their opposing and lateral neighbours — ‘ Cribrimorphs ’— can be predicted with certainty, though the details vary in every lineage. Further calcium carbonate is laid down in connection with (1) the spines that form the intraterminal front wall—the coste ; (2) those that surround the aperture—the ‘apertural spines’ (considered with the first pair of cost, those which bound the aperture proximally, and, fused, form the ‘apertural bar’); and (3) the extraterminal front wall, finally filling up the interzocecial angles; and the process may take place in one or more of these directions simultaneously in any lineage. The first method results (with various modifications in various lineages) in a solid, arched, intraterminal front wall; the second (with various interfusions of the apertural spines and apertural bar, often complicated by one or more pairs of avicularia entering into the structure) in a secondary aperture; the third, again often complicated with avicularia, in a generalimmersion of the zocecia beneath interzoecial walls. The secondary aperture may be prolonged after the manner of a tubular fossil (an interesting case of a primitive method revived); but in some lineages the rims of the secondary apertures spread, especially proximally, and, meeting with their neighbours, fuse to form a secondary front wall (lamina peristomica* of Jullien) above the | general zoarial level. Such forms—‘ Steginomorphs ’—though be- longing to various lineages, are generally placed in d’Orbigny’s genus Steginopora, which, thus used, is seen to be a stage in evolution instead of a genus founded on d’Orbigny’s genotypes. It is inconceivable that Steginomorphs can have any evolutionary future. In extreme cases they present externally a thick crust of calcium carbonate pierced here and there by holes representing apertures and avicularia, that tend to become smaller and more choked as more calcium
1 For these terms see Lang, 1914, GroL. MaG., Dec. VI, Vol. I, p. 6. 2 Jullien, 1886, Bull. Soc. Zool. France, Vol. 11, p. 609.
Professor Percy Kendall—Glacier Lake Channels. 77
carbonate is laid down. So the cingulum of Trepostomes marks the senility of the race, and the Paleozoic Polyzoa fell a victim to the same disease as those Cretaceous forms which, owing to their calcareous skeletons, have been preserved to us to study.
VIl.—Guacter Lake CHanneEts. By PERcY FRY KENDALL. (Concluded from the January Number, p. 29.)
AVING shown that the ‘railway-cutting’ valleys of the Goathland area exhibit anomalies of position seemingly irrecon- cilable with the view supported by Professor Bonney that they are vestiges of an ancient river-system that has undergone readjustments -by the process of stream capture, I may now enforce the argument by exhibiting the contrast between the form and magnitude of the
old and those of the new valleys in the same district.
Sections across the Overflow Channels on Murk Mire Moor. (The datum in each case is 500 feet O.D.)
The sections figured show the general relations of the two channels on Murk Mire Moor to the valley of the Murk Esk, but for a comparison of their respective magnitudes it would be necessary to extend the slope on the right hand down to a level below 200 feet. At the 500 feet contour the Murk Esk Valley is about three-quarters of a mile wide, and the area of the section below this level over a million square feet. At 725 feet, the level at which the upper channel was begun, the area of the section i is, roughly, 43 millions of square feet. If Professor Bonney’s explanation of the deserted channels be adopted it must be admitted that subaerial denudation had failed to obliterate or even to modify to any serious extent their
78 Professor Percy Kendall—Glacier Lake Channels,
contours during the great lapse of time demanded for the excavation of the wide and very deep valley that is presumed to have usurped their functions.
The preservation of the contours of these deserted trenches is, next to their anomalous relations to the relief, their most marked characteristic, and it has furnished the strongest argument yet advanced for the brevity of post-Glacial time.
Whether excavated in granite, volcanic rock, slate, grit, sandstone, conglomerate, limestone, shale, or glacial materials, they show in a large proportion of cases scarcely any appreciable signs of weathering; the salient upper edges are only slightly guttered and the re-entrants at the foot of the ‘ batter’ only rarely are filled in by the running down of the banks. Exceptions to this rule are, however, not negligible, neither are they without significance. There are in Yorkshire, as is well known, several boulder-clays distinguishable by colour, superposition, and contents; they have, as I hope to show some day more fully, a geographical distribution of great interest: (1) the lowest, the Basement Clay, is not recognizable far from the coast, though representatives probably exist in many inland situations ; (2) the Purple Clay, represented in the country west of the Chalk Wolds of Lincolnshire by the Chalky Boulder-clay ; and (3) the Hessle Clay. The last appears to be limited to the seaboard of Yorkshire and the Vale of York, but an equivalent stage cf glaciation is recognizable in the valleys draining the eastern slopes of the Pennines from Swaledale to Airedale.
A long interval marked by widespread and drastic denudation of the earlier deposits intervened between the Hessle stage and that which preceded it, and it seems probable that a great and general retreat and readvance of the ice took place in this interval. The maximum extension of the ice at the Hessle stage was many miles, and in some areas even scores of miles, short of that attained by the ice of the Chalky Boulder-clay, besides which, in the coast region the direction of its onset was different, the north to south component being preponderant, whereas at the earlier stage the impulse seems to have been directed more from the north-east.
The limits of this readvance in Yorkshire can usually be traced with precision and clearness, in some places by well-defined moraines, in others by lake channels. The correlation of these two opposite classes of phenomena, the one an effect of deposition, the other of erosion, is comparatively easy—each forms the approximate boundary between a region in which the glacial deposits form an almost continuous mantle with the characteristic topographic features due to glaciation very fresh and complete, and areas in which the glacial deposits are reduced to a series of shreds and patches, often with long intervening spaces of driftless country. It is interesting to note that just as the Vale of York is spanned by the two great terminal moraines at York and Escrick respectively, so along the lower slopes of the Pennines two principal sets of channels trench the spurs between the river valleys. The upper set of channels is much shallower than the lower, whence it may be inferred that the extreme extension of the ice was rather ‘‘touch and go”’, and that a relatively
Professor Percy Kendall—Glacier Lake Channels. 79
rapid shrinkage brought down to a condition of equilibrium that was maintained for a long period.
The distribution and state of preservation of jake channels is interestingly related to the several drift sheets. Within the area occupied by the ice at the Hessle stage the channels are generally in a very perfect condition, all their contours are sharp and intact; outside this area, but still within the glaciated region, are traces of half obliterated channels such as those detected by Mr. Lower Carter in the valleys of the Don and Dearne. Finally, in the area that altogether escaped the ice invasion these anomalous valleys are, I believe, entirely absent, a fact that finds no explanation in Professor Bonney’s courageous hypothesis.
The facts I have set forth appear to me to render it in a high degree improbable that the channels on Murk Mire Moor can be of any great antiquity—certainly not deserving even the qualified and indefinite reference to ‘‘ post-Jurassic, if not post-Cretaceous’’; and the fact that, like other ‘‘ certain channels”, of which I have seen many hundreds, they are not filled with, or even occupied by, glacial deposits, while the great adjacent valleys of the Esk and Murk Esk contain enormous accumulations of boulder-clay and glacial gravels, seems incompatible with their existence in pré-Glacial times. What- ever the agent that deposited the boulder-clay, whether, as I believe, it was moving land-ice, or whether, as Professor Bonney at one time thought, it was an ice-encumbered sea, it is hard to understand how channels far below the elevation reached by the Drift deposits in the neighbourhood could, if pre-existent, have escaped an infilling of glacial stuff. Mr. Bernard Smith has remarked that some channels are actually excavated in the drift deposits themselves, which seems decisive, for, to adapt an illustration of Hugh Miller’s, the graves cannot be older than the graveyard.
I now return to an argument employed in the first portion of this - communication, namely, that based upon the systematic arrangement of the channels.
Cleveland is only one of many districts in which channels of the same type have been detected. At the risk of prolixity I must mention several: the Pentlands and Lammermuirs(1)!; Cheviots (2); the Wansbeck and Coquet (3); Tyne, Wear, and Tees (4); the Cross Feil escarpment (5); Swaledale; Wensleydale; Nidderdale; Wharfedale, and Airedale (6); the Hambleton Hills; the lower slopes of the Pennines from Masham to Tadcaster (7); the basins of the Don and Dearne (8); the Yorkshire Wolds (9); the Lincolnshire Wolds (10); Black Combe (11); the Forest of Bowland, East
* (1) Kendall & Bailey, Trans. Edin. Roy. Soce., vol. xlvi, pt. i, No. 1, 1908; (2) Kendall & Muff, Trans. Edin. Geol. Soc., vol. viii, 1903; (3) Smythe, Trans. Nat. Hist. Soc. Northumberland and Durham, N.s., vol. iii, pt. i, 1908; (4) Dwerryhouse, Q.J.G.S., vol. lviii, p. 572, 1902; (5) Kendall, Naturalist, 1912; (6) Jowett & Muff, Proc. Yorks. Geol. Soc., vol. xv, p. 193, 1904; (7) Kendall, Brit. Assoc. Rep., 1896; (8) Carter, Proc. Yorks. Geol. Soc., vol. xv, p. 411, 1905; (9) Kendall, ibid., p. 493; (10) Kendall and Carter, Proc. Geol. Assoc., vol. xix, p. 114; (11) Smith, Q.J.G.S., vol. lxviii, p. 402, 1912; (12) Jowett, Q.J.G.S., vol. lxx, p. 199, 1915.
80 Professor Percy Kendall—Glacier Lake Channels.
Lancashire (12); the western edge of the Pennines from Rochdale to North Staffordshire, besides many districts in the North of Scotland.
I have personally examined the great majority of these to the number of several hundreds of individual channels and on lines of country extending to much more than a thousand miles. When these are plotted upon or are compared with the maps wherewith various authors have illustrated their conclusions (deduced from other classes of facts) respecting the course of the old ice-sheets, it is found that with few exceptions.the channels are in the positions that would, upon such a theoretical basis, be assigned to channels draining lakes dammed up by the ice-margins. More than this, they exhibit a consistent fall towards the ice-free country. To regard this correspondence as merely fortuitous would surely be to rack ‘‘ the long arm of coincidence’’ to dislocation point. One may start from Edinburgh and follow an early continuous succession of channels (not, however, of the same period), all sloping in the line of route, almost to the Wash, and if, as I suspect, the through-valley at the common source of the Little Ouse and the Waveney at Lopham’s Ford, near Diss, be an overflow channel from the time when the Hessle Clay ice-front stood about Cromer, then the final release of the East Coast drainage must have been by the Straits of Dover.
To such an orderly and consistent system of drainage I know in all the areas enumerated but one unexplained and at present unexplainable exception, namely, the channel at Moor Close Plantation, Robin Hood’s Bay. Itis a depression quite shallow and innocent-looking at the upper end, but rapidly deepening into an extremely fine gorge. By the irony of fate, not only did this escape my scrutiny when working over the Cleveland district, although I crossed its evanescent upper end several times, but, oddly enough, Professor Bonney’s itinerary indicates that he traversed its length, yet neither he nor I noticed that 2¢ slopes the wrong way and outfalls below the level of any possibly related system.
I summarize the principal objections to Professor Bonney’s explanation of these remarkable channels as relics of a very ancient drainage system possibly antedating the Cretaceous period :—
1. Their restriction to the glaciated parts of our country.
2. Their ‘railway-cutting’ contours prove them to have been produced by large volumes of water.
3. The evidence of their production at a very recent epoch.
4. The way in which they traverse watersheds and their indifference to the geological structure of the country.
5. The continuity of the direction of their ‘ fall’ through wide tracts of country.
6. The discontinuity of the slope where wide gaps occur in the sequence.
7. The occurrence of aligned sequences along the face of escarp- ments and along both sides of a river valley.
8. The occurrence of many parallel channels trenching a single spur.
9. Their occurrence in glacial deposits, though this goes more against the date than the mode of formation.
10. The rarity of any infilling of boulder-clay.
Reviews—Dr. J. W. Gregory’s Geology of To-day. 81
On the contrary hypothesis that these channels were produced by the outflowing waters of temporary lakes upheld by an ice-barrier, all these phenomena find an explanation, and the lakes themselves could in most cases have been predicted from the positions of the ice-margins that were deducible from other classes of evidence.
I do not overlook the fact that there are two fundamentally antagonistic explanations of the ‘ Drift’ phenomena—the Land-ice theory and the ‘Great Submergence’, but whichever of these interpretations be the right one, neither is compatible with the ‘river-trespass’ hypothesis. On the other hand, I have long thought that the study of these ‘‘ certain channels’? did administer the merciful and much needed coup de grdce to the ‘Great Submergence’.
REV Lew s-
I1.—Groroey or T'o-pay: a popular introduction in simple language. — By J. W. Greeory, F.R.S., D.Sc. 8v0; 328 pp., 26 plates. London :.Seeley, Service & Co., Ltd., 1915. Price 5s. net.
HIS is one of a series, ‘‘ The Science of To-day,” intended to be at once advanced and popular: advanced in the sense of being abreast of the latest facts and theories, popular as being intelligible to those unfamiliar with technical modes of expression. ‘‘ Geology,” as the author fully recognizes, is a big mouthful; ‘“‘a full digest of modern geology would be impossible in the space of a book of this size, and it would also be comparatively useless to a general reader.” This being so, 1t is surprising that the author or the editor, if there be such a person, should have weighted the subject by the inclusion of paleontology, by which we do not mean such account of ‘‘ The Age of Trilobites”’, ‘‘The Age of Graptolites’’, and so forth, as is contained in ‘‘ Part III, Historical Geology’’, but rather the more biological aspect of the science that is headed ‘‘The Story of Life on Earth” and constitutes Part IV. This could easily and naturally have been expanded to form an independent volume in the series, thus leaving space for the more adequate treatment of certain strictly geological questions, which in the book as it stands are discussed too briefly or not at all. For instance, the excellent chapter on the Age of the Earth contains no reference to that most fascinating method of investigation provided by pleochroic haloes; and, even in such historical _ geology as there is, one would have expected a reference to the remarkable Middle Cambrian fauna described by Walcott from British Columbia and supposed also to have been detected in our own Islands. Let it none the less be admitted that if, in ‘‘the round world and all that therein is”’, the author has shouldered too Atlantean a burden, he has none the less borne it right well. Professor Gregory is one of the very few geologists of the present day who has attempted, or at least attempted with any success,.to carry on the traditions of the heroic age. ‘l'o him the description of a new species of microscopic fossil comes as easily as the survey of an unexplored continent; the forces that fashion the globe are as familiar to his pen as those that determine the shape of a sea-urchin; from Eozoon to Eoliths nihil DECADE VI.—VOL. III.—NO. II. 6
82 Reviews—Dr. J. W. Gregory’s Geology of To-day.
a se alienum putat. In serious research this spreading of one’s self is apt to make tne result rather thin, with holes too easily picked ; but in a work of the present kind comprehensive knowledge and broad views are all to the good. With this capacity Dr. Gregory combines many years’ experience of lecturing to all sorts and conditions of men, and the facile touch of the ready writer. There are authors who would have been more cautious and exact, others whose style would have lent greater distinction to a narrative deserving of the highest literary skill; but taken on the whole we doubt if any man living could have made a better job of it for the public, the publishers, and himself.
A few improvements may be suggested. The relation of fiords and foldings to the rotation of the earth (p. 153) is expounded more securely than in the author’s recent book on the subject, but is far too condensed for the general intelligence. The statement on p. 307 that the sub-Crag implements prove the presence of pre-Glacial man in this country is not very easily reconciled with the conclusion (p. 817) that ‘‘the geological history of man is confined to the Pleistocene Period’, and that paleoliths are not likely to be found below the Boulder-clay; Dr. Gregory may be right in claiming that much of the Red Crag has been redeposited (‘‘ when” is another matter), but can he claim the whole of the Norwich Crag series as Pleistocene? Few, even amongst the most mechanistic of philosophers, will be found to agree that ‘‘ all the definitions of life and of vitality apply to the more complex forms of crystal growth” (p. 234); perhaps Dr. Gregory does not sufficiently realize that life is a property, not of a certain form of matter, but of an organism. If the wind that rounded the grains and cut the pebbles of the Torridon Sandstone was dry, its dryness may have been due to cold or to passage over an ice-field; we cannot ‘‘safely conclude that the North Atlantic was not then in existence” (p. 194). In Dinotherium it is not the canines but two incisors of the lower jaw that are bent downward (p. 279). On p. 192, Atikokamia, from a Lower Eozoic limestone in Canada, is accepted as a fossil, but there are respectable geologists who regard it as of inorganic origin. Dr. Gregory kindly gives the etymology of generic names: he may like to note that the Greek for a beast is Oyp, for moss (or mossy seaweed) Bpvov, =bryon not brion; that Megalania does not mean the big butcher, but is derived from j\ayw, 1 roam; that ‘‘bent-jaw” is Camptognathus, but that the name he wants is Compsognathus, meaning ‘‘ elegant jaw’. ‘‘Mont Pelée” is a false concord. The English grammar also has suffered, probably from too rapid proof-reading.
The illustrations deserve a word of praise, but it should have been pointed out that the setting of Karl Hagenbeck’s reproductions of extinct saurians is, from the nature of the case, not so appropriate as the backgrounds which Miss A. B. Woodward has given to her ‘vigorous sketches of similar monsters. More reference might have been made in the text to some of the plates. The striking frontispiece —a statue of Agassiz pitched head-first through a stone pavement— will help to sell the book, but we can find no further reference to it and no explanation except that some-one or some-thing ‘“‘upped with
Reviews—Dr. van Hoepen—Stegocephalia, Senekal. 88
his heels”. Does the public realize that in Californian, unlike Scottish, universities earthquakes are more usual than undergraduate Claes.) 2
One does not look to a book of this kind for original observations or ideas, and it is in fact difficult for a reviewer whose knowledge is less exhaustive than that of Professor Gregory to decide when an opinion is taken from elsewhere, or when it has just left the writer’s fertile brain. The comparison of the Old Red Sandstone to the shingle rivers of New Zealand (p. 204); the solution of the difficulty in correlating American, British, and Scandinavian glaciations by a bold denial of any synchronism at all (p. 281); the ‘‘ explanation of the simultaneous extinction of many different kinds of animals” as due to-a reduction in their rate of breeding ‘‘ by slight changes in climate and food-supply that occurred at periods of great geographic change’’ (p. 293): to select these ideas as novelties may be only to expose one’s lack of learning. Fortunately the knowledge of every man, even in his own science, is always less than his ignorance; so that the most learned geologist may well profit by a reading of this popular summary.
II.—SrreocepHaria or Sunexat, O.F.S. By Dr. E. C. N. van Horpen, M.I.
HE material described in this paper is of very great importance, because it represents the only satisfactorily preserved large rachitomous Stegocephalian of Upper Permian age yet found. Dr. van Hoepen’s excellent description is unfortunately marred by his unsatis- ‘factory illustrations. These are rather poor half-tone blocks of photographs and, as always, fail to show the really interesting structural details. Uyriodon senekalensis, as the form is called, is a large animal of a flattened body form, with short and rather feeble “limbs. The skull is only partially preserved, the important occipital region being largely missing. The exoccipital and basi-occipital appear to be extremely similar to those of Hryops, but it seems to the reviewer that the bone described as the basisphenoid is really only the posterior end of the parasphenoid, from which it is said to be indistinguishable. In Hryops the basisphenoid is a very spongy bone, whose lower and lateral surfaces are completely sheathed by the parasphenoid, which even forms a large part of the basipterygoid processes, the cores of which are, however, formed by the cartilage bone. In a Triassic type near Capztosarus, and apparently in that animal itself, the basisphenoid is only represented by a small very spongy ossification round the sella turcica, and the pterygoids unite by suture with the edge of the flat expansion of the back of the parasphenoid. Judging from the description and figure, Myriodon in this region is an exact intermediate between the Lower Permian Hryops and the Triassic forms.
The description of the lower jaw corresponds with that which the reviewer arrived at when, through the kindness of Dr. v. Hoepen, he had an opportunity of examining it. At that time, before the real structure of the Stegocephalian mandible, as described by Professor
84 Reviews—Dr. van Hoepen—Stegocephalia, Senekal.
Williston and Dr. Broom, was known, the reviewer was puzzled by certain appearances which it is now clear are probably to be explained by the presence of a post-splenial and a precoronoid. The reviewer now knows that a post-splenial is present in ‘ Bothriceps’ hualeyz, and that the large bone interpreted by him as the coronoid in Micropholis is really the same bone. It probably occurs also in Batrachiderpeton and ‘ Loxomma’, though the evidence here is not yet clear. The vertebral column is similar to that of Zryops, and the tail is fairly long.
The shoulder-girdle has widely expanded clavicles and interclavicle, as in the large Triassic forms and in the small Permian Zrimerorachis and ‘ Bothriceps’ huwleyi. There is a cleithrum, which, as shown in the useful text-figure, caps the scapula as it does in Hryops. The scapulo-coracoid is structurally similar to that of Hryops, but the scapular portion is far shorter and makes a much more pronounced angle with the coracoidal end. The reviewer remembers seeing a suture between the precoracoid and the coracoid, and may perhaps mention here that he owes to the generosity of Professor Case a young scapula of an Eryopid which shows that the precoracoid was a separate bone forming part of the glenoid cavity, just as in Deinetrodon. The glenoid cavity has the peculiar screw shape common to primitive reptilia and Stegocephalia.
The bones of the fore-limbs are generally similar to those of Eryops, but the author inclines to the belief that the humerus was much less twisted. The humerus of Mastodonsaurus, though other- wise similar to that of Hryops, is less twisted and may have resembled that of Dyriodon.
There are stated to be only two ossified carpals and only four metacarpals; as this is a point of very great importance, and as Eryops and Cacops seem to have five fingers, it is desirable that a definite statement of the evidence should be published.
The pelvis is generally similar to that of Hryops, the relation of the ilium to the sacral rib being the same in both: it is, however, perhaps still more similar to that of Mastodonsaurus when stripped of the addition of an ischium and a scapulo-coracoid with which it is provided in the familiar restoration.
The hind-limb is similar to that of Hryops, so far as the latter is known, but it is very unfortunate that Dr. van Hoepen has not published a figure of the well-ossified and extremely interesting tarsus with five or six tarsals of which he gives a description.
The reviewer some time ago suggested that the large Triassic Labyrinthodonts were derived from large Permian rachitomous forms, and these from the large Embolomerous amphibia of the Coal- measures; all subsequent work, both by other authors and by the writer, has tended to support this view: in particular the very interesting demonstration by Professor Williston that Zrimerorachis, which had been generally supposed to he the most primitive of the Texas amphibia, is really a specialized secondarily aquatic type, has removed a stumbling-block and added an important new idea. The writer regards Eryops as on the whole a neutral and perhaps in some ways a conservative animal.
-
Reviews—Dr. van Hoepen—Stegocephalia, Senekal. 85
In the reviewer's opinion the evolution in the large amphibia took the following course. ‘The amphibia were derived from unknown ‘Crossopterygian’ fish which, like all known members of that group, had a trunk of circular section and a somewhat depressed snout. The skull with the lower jaw formed a mass as high as wide
.at the neck, asin Maw’s uncrushed ‘ Zoxvomma’ skull.. The body was long (more than twenty-nine presacrals in Pteroplax ?), and the tail probably even longer ( Pholidogaster and Cricotus). The animals, as shown by the grooves for lateral line organs on the skull, were mainly aquatic. In Lower Permian times, whilst retaining their round body, they became largely terrestrial (Hryops and especially Cacops and allies), the lateral line grooves becoming obscure or absent.
Subsequently, for some cause of whose nature I can make no suggestion, the head and anterior part of the body began to become depressed, the process culminating in such extraordinarily flattened forms as Cyclotosaurus. Concurrently the animal became secondarily aquatic. Many changes in the skull are correlated with this depression ; of these the most important are: (1) The gradual dorso- ventral thinning of the basiscranii, which leads to the almost complete suppression of the basi-occipital and basisphenoid, to the replacement of the single basi-occipital condyle of the early forms by the paired exoccipital condyles of later types, a process in which many stages are now known, and to the gradual replacement of stout basipterygoid processes of the basisphenoid by thin but necessarily broader expansions of the parasphenoid. (2) The gradual expansion of the interpterygoid vacuities from small slits in the Carboniferous forms to the enormous openings in Cyclotosaurus. Not so obviously correlated with the depression of the skull is a gradual shortening of that part of the pterygoids and of the quadrates, squamosal, etc., connected with them, which lie behind their articulation with the basiscranii. This results in the exoccipital condyles forming the extreme posterior ‘points of the skull in many Triassic types.
‘The primitive Carboniferous amphibia had an embolomerous column in which the pleurocentra and intercentra are perforated discs of nearly equal size; reduction of the upper part of the intercentra and of the lower part of the pleurocentra leads easily to the rachitomous type found in Permian forms: still further reduction of the pleuro- centra with a concurrent strengthening of the intercentra leads to the stereospondylous column found in the Triassic animals (there is unsatisfactory evidence in the Stuttgart Museum suggesting the occurrence of small pleurocentra in Mastodonsaurus and DMetopo- saurus). The clavicles of the typical Carboniferous embolomerous Pteroplaz are flat plates with parallel anterior and posterior margins very like those of the fish Megalichthys. he interclavicle is a very small rhomboidal bone with a rudimentary posterior stern. In the more terrestrial Lower Permian types, e.g. Hryops and Cacops, the upper end of the clavicle is narrowed and affixed to the front edge of the scapula, separated from it, however, by the cleithrum, and the interclavicle becomes proportionately larger. In the Triassic forms, in correlation with the depressed form of the head and anterior part of the body and probably with the aquatic habits, the lower end of the
86 Revews—Dr. van Hoepen—Stegocephalia, Senekal.
clavicle and the interclavicle become enormously expanded into the great bony plates so familiar in Metoposaurus and other types. The upper end of the clavicle, however, retains the slenderness and lack of ornament which it acquired in the Lower Permian terrestrial stage. Beyond a reduction in size necessitated by the flattened body the scapulo-coracoid remains essentially unchanged throughout the series of changes, and the fore-limb itself is only slightly altered, being smaller and more feebly ossified in later types. If Dr. v. Hoepen is correct the number of fingers is reduced to four and the humerus becomes less twisted. Except a slight weakening no change seems to take place in the hind-leg and its girdle.
From the foregoing account it will be seen to how large an extent the evolutionary changes in the temnospondylous amphibia depend on two causes, the gradual flattening of the animal and its gradual return to an aquatic life. Study of the perfect materials in the Walker Museum, under Professor Williston’s charge, and in the American Museum, have considerably strengthened my belief in the close relation of Ceraterpeton, Batrachiderpeton, and Diplocaulus, animals whose ancestors have not been connected with the temnospondyl stock since very remote times. If these three creatures do really form a morphological family, then we have direct evidence that a similar flattening and return to the water have produced identical changes quite independently in two quite distinct amphibian stocks. In any case, even if the three animals mentioned above be not related, the resemblance in structural details between Deplocaulus and the Stereospondyls, which is very marked, must be due to convergent eyolution, because whilst Dzplocaulus is Basal Permian the stereo- spondyl structure did not arise till the Trias. The occurrence of four fingers in Myriodon whilst Eryops has five is another remarkable convergence to other amphibian stocks.
We have thus direct and very strong evidence that two quite distinct groups of amphibia, separating very far back, have inde- pendently pursued similar evolutionary paths at quite different rates. We have seen that in both cases these changes can be referred back to a general flattening, and then the secondary adoption of an aquatic life. No trace of these trends can have been visible when the two lines separated, for, in one case at least, their origin must have followed the adoption of, and necessary adaptation to, a primarily terrestrial existence. This fact is only a particular case of a quite general feature of evolution, that allied stocks tend to pursue a similar course of change, the same and often striking new departures being initiated in diverse lines long after their separation, not necessarily at the same time or in the same order. Students of paleozoology have long been familiar with this fact, which is perhaps the most vital contri- bution to evolutionary data made of recent years, and it is interesting to see that botanists are now recognizing a similar ‘‘phyletie drift” in the subjects of their study, although zoologists and especially those whose work has dealt with the experimental study of evolutionary factors have so far paid little or no attention to it. M. H. Bergson’s philosophy, so far as it concerns biology, seems to depend on a super- ficial and incomplete appreciation of this great fact.
Reviews—Economie Geology of Canada. 87
The importance of Myriodon lies in that it provides a useful intermediate stage between Zryops and the Triassic forms.
D. M.S. Watson.
I1].—Tan Economic Grotogy or CanaDa.
IW\HE coal-fields of Manitoba, Saskatchewan, Alberta, and Eastern
British Columbia are described in Memoir 53 of the Geological Survey of Canada, and those of British Columbia as a whole in a later memoir (No. 69), both by D. B. Dowling. The coal horizons range from Lower Tertiary to Cretaceous over the whole area covered by the two memoirs. In character the coals grade from lignite to true coal in undisturbed strata, and from coking coal to anthracite where the rocks have undergone considerable movement. In another memoir, No. 59, Coal Fields and Coal Resources of Canada, by D. B. Dowling, we learn that the great Dominion has by far the largest reserve of coal in the Empire, estimated at no less than 1,234,269 million tons; but most of it is lignite and brown coal, and is not available for commerce since it is as yet remote from profitable markets. Important supplies, however, occur on both the Atlantic and Pacific seaboards, and are able to compete with foreign fuel.
The Canadian Department of Mines issues a publication on ‘Products and By-Products of Coal’’, by KH. Stansfield and F. E. Carter, which brings together in a compact and practical form useful information as to the methods of producing coke, gas, ammonia, and tar, from bituminous coal, and the properties and industrial uses of, these materials. The deplorable war conditions in Europe have made some of these products, especially coal-tar dyes, scarce in Canada; but while the demand in Canada is not sufficient to establish this industry on a profitable basis, it is shown that the production of certain other important by- -products of coal is peculiarly suitable for
_ Canada, and the Dominion could be rendered less dependent on foreign sources of supply.
‘The results of the testing of six lignite samples from Alberta are given in a further publication of the ‘Department of Mines, by B. F. Haanel and J. Blizard, an instalment of an investigation of all the coals of Canada with a view to determining their best industrial uses. ‘he Albertan lignite isshown to be well adapted for utilization in the gas producer.
Another interesting publication of the Department of Mines is a Report on the “‘Salt Deposits of Canada and the Salt Industry”’, by L. Heber Cole. The only salt deposits at present being exploited are those located in Ontario, which occur in the Salina formation (Silurian), but saline deposits are known to exist in Northern Manitoba and the Mackenzie basin of Alberta. These may be exploited as soon as these districts are opened up by railways, and may then supply the western provinces, which have now to pay high freight rates on their salt supply. The technology of salt manufacture is exhaustively described in the second part of the report.
The clay and shale deposits of Quebec are dealt with in a preliminary report (Memoir 64, Geological Survey of Canada), by
88 Reviews—G. F. Becker—Isostasy and Radioactivity.
J. Keele. Stratigraphically the clays now exploited range from the Pre-Cambrian to the Pleistocene ; but while there is a lack of high- grade clays like fireclays or pottery clays, there is an abundance of material suitable for the manufacture of rough clay products. The report contains valuable chapters on the origin and properties of clay, the effects of heat in clays, field examination and testing of the materials, and on methods of mining and manufacture, written mainly for the non-geological reader.
Memoir No. 74 is ‘* A List of Canadian Mineral Occurrences’’, by R. A. A. Johnston. The bulk of the book is occupied with the names of the minerals arranged alphabetically, with notes as to their occurrence under the heading of each province. The second part gives the names of provinces and their divisions in alphabetical order, with the list of minerals found in each area appended. The work is an exhaustive compendium of Canadian mineralogy.
IV.—Isostasy anp Rapioacriviry. By Grorex F. Becker. Bull. Geol. Soc. Am., vol. xxvi, pp. 171-204, March 31, 1915. FY\HE object of this paper is to draw attention to certain alleged
discrepancies between recent developments in the theory of isostasy, and the age of the earth as determined by radio-active methods. Dr. Becker returns to his own method of calculating the age of a cooling earth, modified by taking into consideration radio-active supplies of heat energy. He assumes that the depth at which the temperature-gradient curve most nearly approaches the diabase curve ‘of fusion, i.e. the depth at which rock fusion is most easily - accomplished, is also the depth of Hayford’s level of isostatic compensation, 121 kilometres. Taking an earth with an initial temperature at the surface of 1,300°C., he finds the age to be 68 million years, radiothermal energy maintaining only one-seventh of the present temperature gradient. If radio-activity supplies two- thirds of the earth’s heat loss, then the age is 1,314 million years, and the depth at which fusion most readily occurs becomes 300 kilometres. Dr. Becker rejects such an earth as being probably incapable of volcanic phenomena.
Professor Barrell (in the papers previously noticed in January last, p. 38) makes out a strong case for the existence of an astheno- sphere, extending perhaps to 600 kilometres below the level of isostatic compensation. He shows that the depth of easiest fusion must be below the level of compensation, and that it is to be looked for in the heart of the asthenosphere, that is, at a depth of about 400 kilometres. Combining this result with Becker’s analysis, the age of a cooling earth becomes considerably greater than 1,314 million years, and the proportion of the earth’s heat maintained by radio- activity becomes much nearer to its probable value—three-quarters, — or more (Grou. Mae., February and March, 1915). Geological deductions from isostasy and radio-activity are thus easily brought into harmony, and the source of the discrepancies alluded to by Dr. Becker are at least as likely to be found in his own interpretation of isostasy as in the simple method of determining the ages of radio- active minerals based on their lead-uranium ratios.
ArrHur Hommes.
Reviews— Whitman OCross—Lavas of Hawaii. 89
V.—Tue Kitonpixe anp YuKon GoLDFIELD.
REPRINT from the Scottish Geological Magazine of a paper by Mr. H. M. Cadell on the Klondike and Yukon Goldfield in 1913 is included in the Smithsonian Report for 1914 (pp. 363-82). The paper-is both of scientific and of economic interest. The absence near Dawson of the signs of glaciation so conspicuous to the south is explained by the extreme dryness of the climate. But for the destructive work of glaciers in the Ice Age placer deposits of gold might have been found in Canada, Scotland, or Scandinavia. At the present time mining in the Klondike needs ample capital. The various ways employed for winning the gold—uincluding the remarkable dredging process, and the hydraulic or ‘ monitor’ method—are fully described and illustrated. About a million pounds worth of gold was extracted in 1913. The life of the field has been stated to be very limited, but there is likelihood of the discovery of paying reefs.
~ VI.—Txe Minerat Resources or THE Puinipprne Istanps FOR THE year 1914. Division of Mines, Bureau of Science, Manila, Philippine Islands, 1915.
HE American administration of the Philippines has naturally led to a steadily increasing exploitation of the mineral wealth of the islands. Gold is by far the most important product, silver, iron, and lead following far behind. Deposits of copper, manganese, and coal have been worked from time to time, but have fallen into quiescence during recent years. Guano is now being mined as a fertilizer, and _ the War has reawakened interest in the manganese ores. A brief account is given of the occurrence of copper ores, associated with andesite, in Zambales.
_ ViI.—Lavas or Hawatt and THEIR ReLations. By Warrman Cross. United States Geological Survey, Prof. Paper 88, 1915.
HE author gives a full account of the petrography of the Hawaiian islands as far asthey are known at present. While the prevalent lavas are olivine basalts, many other types are represented, notably picrite basalt, bronzite basalt, trachydolerite, oligoclase-bearing lavas (e.g. kohalaite), soda-trachyte, nepheline basalt, and melilite basalt. This association indicates that the division of rock types into ‘ Atlantic’ and ‘Pacific’ facies is inappropriate, and further that alkalic and calcic magmas may be derivatives from a common source. The lavas of Tahiti, Samoa, and Réunion illustrate very similar associations. The author discusses various processes of differentiation. He declines to admit Daly’s view that the more basic lavas tend to issue from lower levels than the lighter ones, and denies that the association of alkaline rocks with limestones has any bearing on the origin of the former. Beyond indicating that periods of decreased activity were favourable to differentiation, and stating his opinion that the processes appear to have acted mainly on the liquid magma, the author advances no suggestions as to the physical mechanism concerned.
90 Reviews—Wabana Iron Ore of Newfowndland.
VITI.—Wasawa Iron Orne or Newrounpranp. By A. O. Hayes. Canada, Geological Survey Memoir 78, 1915.
N this beautifully illustrated memoir a detailed account of the I stratigraphy and petrology of the Lower Ordovician oolitic iron- ores of Wabana is placed on record. An unusually complete series of analyses has been made, confirming the petrographic identification of the chief minerals present—hzmatite, chamosite, and siderite. The writer concludes that the iron-ore occurs as a primary bedded deposit in a series consisting mainly of shales and sandstones. Pisolitic iron- ores have been found in the Llandeilo of Wales by W. G. Fearnsides, who, however, has urged their probable metasomatic origin. The writer gives a summary of the occurrences of other iron-ores of similar character, and notes the varying interpretations of their mode of origin, some authors favouring original precipitation, others holding the replacement theory.
IX. Sxippaw.—In the Proceedings of the Liverpool Geological Society (xii (2), 1915), Mr. Jas. W. Dunn gives the results of many years work on Sheet No. 101 8.E. (Geol. Survey, 1 inch). He does not draw up any conclusions, so we must refer the reader to the paper for the petrology, with which it largely deals.
REPORTS AND PROCHEHDIN GS.
Liverroort GronocicaL Socrery.
December 14, 1915.—J. H. Milton, Esq., F.G.S., F.L.S., President, in the Chair.
The following paper was read :—
‘‘On the Igneous and Pyroclastic Rocks of the Berwyn Hills (North Wales).”’ By the late Thomas Henry Cope, F.G.S. Edited by Charles B. Travis. ;
This paper represents the results of the work of the late T. H. Cope, F.G.S., during many years, supplemented by contributions by the editor. The area described, about 150 square miles in extent, includes portions of the counties of Denbigh, Merioneth, and Mont- ‘gomery. The sedimentary formations present range in age from the Llandeilo to Upper Tarannon and Llandovery, and have been subjected to cross-folding at two periods of time widely separated, giving rise to a periclinal dome which has been greatly denuded.
The igneous and fragmental rocks, to which attention has been chiefly devoted, occur at various horizons in the Ordovician sediments, and comprise acid and intermediate lavas, intrusive sheets of inter- mediate and basic composition, and acid and intermediate fragmental deposits. ‘The most important pyroclastic rocks are three strongly marked bands of rhyolitic tuffs and agglomerates (‘‘ Peripheral Series”’), of Upper Bala age. They are traceable most clearly on the northern and western margins of the district, and correspond to the ‘‘ Ash Beds ”’ of the Geological Survey. In the southern portion
Reports & Proceedings—Liverpool Geological Society. 91
of the area, near Llangynnog, in the Tanat Valley, four bands of spherulitic rhyolite occur, associated with acid tufts (‘‘ Lower Tuffs’’). They occupy a stratigraphic position at the base of the Bala series, and are correlated with the Snowdonian lavas of the Capel Curig — Dolwyddllen group.
On the extreme easterly margin andesitic lavas and tuffs have been extruded from local vents, of which remnants are recognized. They comprise a series of hornblende-porphyrite, pyroxene, hornblende, and enstatite-andesites, with tuffs, breccias, and agglomerates of similar composition. These lavas represent the latest phase of eruptive activity in the Berwyn area on or above the horizon of the Bala Limestone, and they are probably related to the andesitic lavas and tufts of the Breidden Hills.
The oldest volcanic rocks of the region lie in the centre of the Berwyn anticline, near Llanrhaidr yn Mochnant (the Craig y Glyn group). They are thin flows of spherulitic rhyolites, interbedded with calcareous acid tuffs, and are petrographically similar to the Llangynnog rhyolitic series, but of much greater age. They are associated with fossiliferous Llandeilo sediments, but it is considered that they may possibly be rather of Upper Arenig age.
The intrusive intermediate series occurs only in the north-eastern and south-western corners of the district, in the valleys of Glyn- ceiriog and the Hirnant respectively. In the former locality the sill has been injected into Bala slates and grits, and overlies the middle tuff band. It isa hemicrystalline, vesicular rock, a keratophyre or soda-trachyte, composed of oligoclase-andesine felspar, pyroxene, and _ secondary products.
The second type forms a series of five intrusive bands, hitherto mapped as voleanic ash, in the much faulted tract south of Llangynnog. These soda-rich rocks are hemicrystalline with an original glassy
base, composed of oligoclase-andesine plagioclase and subordinate "pyroxene, now represented by pseudomorphs and interstitial chlorite. The structure varies from variolitic to insertal. The rocks resemble certain tholeiites, but do not correspond exactly with any rocks hitherto described, and have accordingly been provisionally termed «« Hirnantite”’.
On the northern and westerly borders and in the central part of the district a number of basic intrusions form well-marked sills in the areas characterized by great dynamic pressure. They are well exposed in the following localities: Pen-y-bont (Llansaintffraid D.C.), Spring Hill (Pandy Glynn), Cwm Dwyll, Carnedd-y-ci (Llandrillo), Cader Berwyn and Llyn-llyn-caws, and Miltir-gerig. They are dolerites in various stages of preservation, frequently bearing analcite, and agree in many respects with the basic sills of Carnarvonshire. They are, however, exceptionally interesting by the evidence of albitization which they present, a process which has not hitherto been recorded for the rocks of North Wales. In one instance (Carnedd-y-ci) albite-dolerite is associated with quartz-keratophyre under circumstances which appear to suggest an example of a composite intrusion.
92 Correspondence—Dr. C. 8S. Du Riche Preller.
CORRESPONDENCE.
THE CARRARA MARBLE DISTRICT (APUAN ALPS).
Srz,—In reply to Professor Bonney’s remarks on p. 47 of the Groroeicat Magazine of January, suffice it to point out (1) that the determination of the age of the crystalline schists and of the marble beds is essentially a question of paleontological and stratigraphical evidence, which, as I have shown, is absolutely conclusive, and is, more- over, universally accepted; (2) that it was neither the object nor within the available space of my paper to enter into the details of micro- scopical examination, the less so as this part of the subject has been exhaustively dealt with in the recent memoirs of Professor d’Achiardi, of Pisa, and of Mattirolo and Franchi of the Italian Geological Survey; (3) that the district of the Apuan Alpsis pre-eminently one which, owing to its extent and complexity, requires long and patient study of the entire area, and cannot be mastered by two admittedly incomplete visits, of only a few hours each, barely beyond one point
of its periphery. C. Du Ricue Preiirr.
EDINBURGH. January 12, 1916.
THE CRYSTALLINE ROCKS OF THE PIEMONTESE ALPS.
Srr,—In a footnote (p. 16) of my paper on the Permian formation of the Maritime and Western Alps in the Gxoxoeicat Macazrne of January, I mentioned that I propose to dealin a subsequent paper more fully with the crystalline schists and the pietre verdi areas, also in relation to the anti-Archzan and pro-Mesozoic views of Franchi as opposed to those of Zaccagna. In the meantime I should perhaps mention that in the most recent Italian geological maps just come to my notice the extensive crystalline cale-schist formation, which up to 1909 figured as pre-Paleozoic, has been rejuvenated to Mesozoic.
C. Du Ricuz PRELLER.
EDINBURGH. January 12, 1916.
Si TAL OPN IS5 Sa 5
ARTHUR VAUGHAN, B.A. (Cant.), M.A. (Oxon.), D.Sc. (Lond.). BoRN MARCH, 1868. DIED DECEMBER 38, 1915. (WITH A PORTRAIT, PLATE V.)
Tur death at the early age of 47 of Dr. Arthur Vaughan, which took place at Oxford on December 8, removes one of the most brilliant of British stratigraphical geologists.
Dr. Vaughan was the son of the late William Vaughan, F.I.A., Actuary to the Board of Trade, and was born in London in 1868. After a highly successful career at University College School, he entered University College, London, in 1885, and there acquired his first interest in geology from the influence of Professor Bonney. In 1887 he entered Trinity College, Cambridge, with an open scholarship,
Grou. Maa., 1916. PLATE V.
ARTHUR VAUGHAN, B.A.(CantT.), M.A.(Oxon.), D.Sc.(Lonp.).
1868-1915
o
Obituary—Dr. Arthur Vaughan. 93
and in his first year obtained a major mathematical scholarship. He was third Wrangler in [890, and in 1891 obtained a First Class in mathematical physics in Part II of the Mathematical Tripos. He also obtained Ist class Honours in Mathematics in the London B.Sc. examination. These academic successes, brilliant though they were, were not considered by his teachers to do full justice to his ability.
On leaving Cambridge in 1891 he accepted a post as Senior Science Master at an Army coaching establishment at Clifton, and remained there till 1910. ~
His earliest papers were on mathematical physics and dealt with the earth’s crust, but shortly after settling at Clifton he became acquainted with "Edward Wilson, then the Curator of the Bristol Museum, and ‘to Wilson’s influence the definitely geological bent of Vaughan’s main work may in a great measure be attributed. Wilson was principally interested in the Jurassic rocks, and it was to these that Vaughan first turned his attention, his earliest geological paper, «The Lower Lias of Keynsham ”’ (1902), being written in collabora. tion with Mr. J. W. Tutcher.
During the years 1900 and 1901 he was engaged in the study of the splendid series of sections exposed in constructing the South Wales direct line between Filton and Wootton Bassett. The strata exposed range from the Old Red Sandstone to the Kimmeridge Clay, and include a fine section of Carboniferous Limestone. It was the study of these latter rocks which induced Vaughan to re-examine the Avon section, and led to the work with which his name will always be associated. His paper on the Carboniferous Limestone of the Bristol Area, which was published in 1905, has already become a ' geological classic, and as regards the wide applicability of the results, _ and the stimulating effect upon other workers, it may confidently be ciaimed that no more important piece of paleontological stratigraphy -has been carried out since Lapworth’s work on the Lower Palzozoic rocks.
. Vaughan’s results at once began to be applied by keen workers in numerous parts of the British Isles, and he himself described the Rush (1906) and Loughshinny (1908) sections in collaboration with Dr. Matley, and that of Gower (1911) with Mr. (now Lieutenant) EK. L. Dixon. The above papers are principally concerned with the zonal succession of the Lower Carboniferous rocks, but deal also with the mutations of Carboniferous Corals and Brachiopods, a subject in which Vaughan quickly became deeply interested. His views on the lines of development in the case of Corals are set forth in a paper on the Avonian of Burrington Combe (1911). |
The rapid growth of interest in the Carboniferous Limestone led to many problems being submitted to him, and instead of spending his spare time in healthy field work he came to be more and more contined to indoor work, which was carried out under none too favourable conditions. He was a man who never spared himself, and it is to be feared that out of the kindness of his heart he undertook much identification with which he really ought never to have been troubled. The duties of an Army tutor are also of a very exacting character, and all this hard work began about 1908 seriously to affect his health.
94 Obituary—Dr. Arthur Vaughan.
In 1905 he became Secretary of the British Association Committee for the investigation of life-zones in the British Carboniferous rocks, and drew up a series of important reports. Particular attention may be directed to those of Winnipeg (1909), Sheffield (1910), and Manchester (1915). In the Winnipeg report he correlated the Carboniferous Limestone (Avonian) succession in various parts of the British Isles, and threw much light on the phasal equivalents, while that at Manchester, his last piece of work, is concerned with the shifting of the western shore-line in England and Wales during the Avonian period. The Sheffield report (1910) correlates the British . and Belgian succession, and was the result of a visit paid to Belgium in the summer of 1909. Vaughan paid a second visit to Belgium in 1912, this time in company with a party of British geologists, and had the satisfaction of completing his Belgian work in a paper published in the Geological Society’s journal last year. The importance of this work was quickly recognized by Belgian geologists, and he was elected a Foreign Member of the Geological Society of Belgium. He received the Wollaston Fund from the Geological Society in 1907 and the Lyell Medal in 1910.
In 1910 Vaughan moved to Oxford, having accepted a post as Lecturer on Geology in the University, and the charm of his personality and his marked ability as a teacher made him very popular with his students. While at Oxford his attention was particularly directed to questions bearing on the evolution of animal life, and breaking new ground he devoted much time to the study of fossil ungulates. He was also engaged on a textbook of paleontology written on somewhat novel lines, for the illustration of which Mr. Tutcher had prepared several hundred photographs. Although this is left unfinished, there is hope that it may prove possible to publish it.
Though his lighter duties at Oxford caused some improvement in Vaughan’s health, it was still the cause of much anxiety to his friends. In 1914 he visited Australia with the British Association, and was able to satisfy himself that the remarkable Permo- Carboniferous strata were correctly correlated with the Artinskian of Russia, He hoped to have the opportunity of visiting Russia for the examination of these strata, and with his usual thoroughness occupied himself during the last years of his life with the study of Russian.
_ Probably the characteristics which impressed themselves most on the many friends who mourn his early death were his geniality and loyalty, the courage with which he stuck to his work through long years of failing health, and the remarkable grip and clear-sighted logical analysis with which he tackled any problem.
S. H. R.
LIST OF PAPERS BY ARTHUR VAUGHAN.
‘‘ Stress within a Sphere due to inequalities at its surface, with application to the Harth ’’: 1897, privately printed, Taylor & Francis.
‘“* The Corrugation of the Earth’s Surface and Voleanic Phenomena’”’ : GEOL. MAG., Dec. IV, Vol. I, pp. 263-70, 1894.
Obituary—Dr. Arthur Vaughan. 95
‘Remarks on Mr. Mellard Reade’s Article ‘On the Results of Unsymmetrical Cooling and Redistribution of Temperature in a Shrinking Globe as applied to the Origin of Mountain Ranges’ ’’: ibid., p. 312.
“Problems connected with a Cooling Earth ’’: ibid. , p. 505.
“The Making of Mountains: A Reply to Mr. Mellard Reade’’ : ibid., Vol. II, pp. 93-6, 1895.
‘The Argument for Solidarity drawn from Ocean Tides’’: Proc. Bristol Nat. Soc., ser. II, vol. viii, pp. 269-73, 1899.
“‘Notes on the Corals and Brachiopods obtained from the Avon Section and preserved in the Stoddart Collection’’: ibid., vol. x, pp. 90-134, pls. i-ii, 1903.
“The Lowest Beds of the Lower Lias at Sedbury Cliff’’: Abs. Proc. Geol. Soc. 1902-3, p. 124; and Q.J.G.S., vol. lix, pp. 396-402, 1903.
“The Paleontological Sequence in the Carboniferous Limestone of the Bristol Area’’: Abs. Proc. Geol. Soc. 1903-4, pp. 100-1, 1904; and Q.J.G.S., vol. xi, pp. 181-305, figs., pls. xxii-ix, 1904.
““Note on the Lower Culm of North Devon’’: GEOL. MAG., Dec. V, Vol. I, pp. 530-2, 1904.
“* Note on the Brachiopods and Corals collected by Dr. Brendon Gubbin from the Carboniferous Limestone of South-West Gower, and the Zones which they indicate ’’: Proc. Bristol Nat. Soc., ser. Iv, vol. i, pp. 53-6, 1905.
*“ The Carboniferous Limestone Series (Avonian) of the Avon Gorge ’’: Proc. Bristol Nat. Soc., ser. Iv, vol. i, pp. 74-168, figs., pls. i-xvi, 1906.
Note on Corals in Report of the Committee on Life-Zones in the British Carboniferous Rocks: Rep. Brit. Assoc. 1906, pp. 309-11, 1907.
““A Note on Semimula’’: Ann. Mag. Nat. Hist., ser. VII, vol. xix, pp. 194-8, 1907.
‘**Note on the Coral-Zones of the eorian (Lower Carboniferous) ’?: Proc. Geol. Assoc., vol. xx, pp. 70-3, 1907.
“A Note on the Carboniferous Sequence in the Neighbourhood of Pateley Bridge ’’: Proc. Yorks Geol. Soc., vol. xvi, pp. 75-83, 1907.
“ Faunal Succession i in the Carboniferous Limestone (Avonian) of the British Isles’: Rep. Brit. Assoc., vol. Ixxviii, Dublin, 1908, pp. 267-9, 1909; vol. Ixxix, Winnipeg, 1909, pp. 187-91, 1 pl., 1910; vol. Ixxx, Sheffield, 1910, pp. 106-10, fig., 1911.
“Note on Clisiophyllum ingletonense, sp. nov.’’?: Proc. Yorks Geol. Soc., N.S., vol. xvii, pp. 251-5, pl. xxxviii, 1912.
‘Correlation of Dinantian and Avonian’’: Q.J.G.S., vol. lxxi, pp. 1-52, pls. i-vii, 1915.
“ The Reef Knolls of Clitheroe, Bowland, and Craven’? (read at the Yorkshire Geological Society, Leeds, June 24, 1915); to be published in the Proceedings of the Yorkshire Geol. Soc. now in the press.
** Shift of the Western Shore-line in England and Wales during the Avonian Period ’’ (read at the British Association Meeting, Manchester, 1915). With E. E.L.Drxon. ‘The Carboniferous Succession in Gower (Glamorgan- shire), with Notes on its Fauna and Conditions of Deposition’’: Abs. Proc. Geol. Soc. 1909-10, pp. 72-3, 1910; and Q.J.G.S., vol. Ilxvii,
pp. 477-567, figs. [geol. map], pls. xxxviii—xl, 1911.
With C. A. Matnry. ‘“‘ An Account of the Faunal Succession and Correlation [of the Carboniferous Rocks of Rush (Co. Dublin)]’’: Q.J.G.S., vol. lxii, pp. 295-322, pls. xxix—xxx, 1906.
— “The Faunal Succession in the Carboniferous Limestone of the South-West of England and Ireland: Interim Report’’: GEoL. Mae., Dec. V, Vol. IV, pp. 466-8, 1906; and Rep. Brit. Assoc. Adv. Sci. 1906, York, pp. 292-3, 1907.
—— .“‘The Carboniferous Rocks at Loughshinny (Co. Dublin)’’: Q.J.G.S., vol. lxiv, pp. 413-74, pls. xlix—l, 1908.
With S. H. REyNotps. ‘‘On the Jurassic Strata cut through by the South Wales Direct Line between Filton and Wootton Bassett, Wilts’’: Abs. Proc. Geol. Soc. 1901-2, pp. 132-3, 1902; and Q.J.G.S., vol. lviii, pp. 719-52, figs., 1902.
96 Obituary—Dr. J. C. Moberg—W. R. Jones.
With S. H. RrEynotps. ‘‘ The Rhetic Beds of the South Wales Direct Line”’ : ibid., 1903-5, pp. 41-2; and Q.J.G.S., vol. lx, pp. 194-213, figs., pl. xviii, 1904.
— ‘‘Faunal and Lithological Sequence in the Carboniferous Limestone Series (Avonian) of Burrington Combe (Somerset)’’: ibid., 1910-11, pp. 94-5; and Q.J.G.S., vol. lxvii, pp. 342-92, figs. [plan], pls. xxviii- xxxi, 1911.
With J. W. TutcHER. ‘‘ The Lower Lias of Keynsham’’: Proc. Bristol Nat. Soc., ser. III, vol. x, pp. 1-55, figs., 1903.
With T. W. VauGHaNn. ‘‘ Notice of H. M. Bernard’s Work on the Poritid Corals (Recent and Fossil)’’: Science, N.S., vol. xxvi, pp. 373-8, 1907.
With others. Excursion to Bristol: Proc. Geol. Assoc., vol. xx, pp. 150-6, pl. iv, 1907.
— Report [as Secretary] of the Committee on the Faunal Succession in the Carboniferous Limestone of the South-West of England: Rep. Brit. Assoc., 1906-10.
PROFESSOR, DR. J.C. MOBERG: Lund University, Sweden.
We regret to learn of the death of Dr. Johan Christian Moberg, Professor of Geology at Lund University and Member of the K. Svenska Vetenskaps-Akademi, which took place at Lund on December 30, 1915. Professor Moberg was well known as a worker in the Paleozoic Geology and Paleontology of Sweden, especially of Scania, and produced a valuable summary of the subject for the use of the Geological Congress when it met at Stockholm. He was in his sixty-second year.
WILLIAM RUPERT JONES. Born 1855. Di=D DECEMBER 17, 1915.
Tue death is announced of the late Assistant Librarian to the Geological Society of London at the age of 60. Mr. William Rupert Jones was the son of the well-known geologist Professor Thomas Rupert Jones, F.R.S., for many years himself Assistant Secretary to the Society. He was appointed Assistant Librarian in 1872, and retired on pension in 1912, having served the Society for forty years.
Mr. Jones acquired during his long service an extensive general knowledge of geological and other literature, and aided by a remark- able memory he was able rapidly to assist authors and inquirers to references in almost any line they chanced to pursue.
For many years his Catalogue of Geological Literature, although confined to that received by the Society itself, was the standard book of reference, from its simplicity and general correctness. And there are many authors who had occasion to appreciate his skill in the production of coloured diagrams to illustrate their papers, a labour which grew up gradually but quite unofficially.
Mr. Jones, who leaves no issue, was buried in Brompton Cemetery.
Erratum.— In the Gzorosrcat Macazine for January, 1916, p. 39, 7th line from foot of page, for ‘repeated substances have taken place” read ‘repeated subsidences have taken place’’.—Ep. Gon. Mae.
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EDITED BY HENRY WOODWARD, LL.D., F.R.S., F.G.S., &c.
ASSISTHD BY Prorrssor J. W. GREGORY, D.Sc., F.B.S., F.G.S. Dr. GEORGE J. HINDE, F RB.S., F.G.S. sin THOMAS H. HOLLAND, K.C.1 E., A.R CASe DSCs EYRE Sts CEU Gs Si: Dr. JOHN EDWARD MARR, M.A..-Sc.D. (Camp.), F.R.S., EF.G.S. Dr. J. J. H. TEALL, MA., Sc.D. (Camp.), LE.D.; ¥F.RB.S., 1A G.S.- - aaa) ~ PROFESSOR W. W. WATTS, Sc.D., M.Sc., F.R.S., Vice-Pras, Gnon dé, (ST) DR. ARTHUR SMITH WOODWARD, F.R.S., Deas), Pix fGuon. Soc,
MARCH, 1916. \
CONTENTS.
I. ORGINAL ARTICLES.’ Page Page oan Challe Polyzoa. By R. M. Fossil Mammals from China... ... 124 : BRYDONE, F.G.S. (Plate VI.) - 97 | Mammothsand Mastodons ... .., 128 : ~ On Lovenia forbesi, Miocene Be ry pip ay 5 ees ROE Ee HANGING. | Effects of Drought in 1 Waterberg . 129 se a G re (win a oe | Climate of Geologic Time ...... 129 a porieean ue Bais 100 The Glacial Anticyelone Pee eo sage Stee : Life of Edward Suess ... . 131 PD (oe = and fdunntitative Bibliography of Yorkshire Geology 131 Bees ee Silurian of Saskatchewan ... 132° yee eee Ce le oe The Fluvio-glacial Gravels et the _ IV. REPORTS AND PROCEEDINGS. ai ee Thames Valley. By R. M. Geological Society of London :.. 132 jf DEELEY, M.Inst.C.E., F.G.S. 111 Anniversary Meeting, sear On the genus Trinucleus. By ISS ALOU Gis toe 135 F. R. Cowrer REED, Sc.D., Geological Society of ‘Edinburgh . 136 F.G.S. aoe Seer a . 118 | Geological Society of Glasgow | 138 SAT. Novices OF eae Geological Society of Liverpool 139 Mineralogical Society ... paper lis%s) HH eterangiums of British Coal- measures. By Dr. D. H. Scott, V. CORRESPONDENCE. IS ~- 123 |: protessor T. G. Beno Spee ee ahhe= Geology “of Poreupine. By 0. Ts ma 142 Pee, ae B. Tyrrell o : ; 94 inne ... ook wee ate ae S He SWE panes suse poy se EAS : \ Ill. See * Geology of Malay States. By J. B. VI. OBITUARY. Poe Ncrivenor = 7 ...... 125 ; Count zu Solms-Laubach ... ... 143 ; _ The Interior of fhe Earth agen Gtr Dire aveall SVE AS oo oes aa
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THE
GHOLOGICAL MAGAZINE NEWASERIES.) DECADE. Vi. VOLE, Ml.
No. III.— MARCH, 1916.
ORIGINAL ARTICLIEHS.
EEO DOE I.—Nores ON NEW OR IMPERFECTLY KNOWN CHALK Potyzoas. By R. M. BRYDONE, F.G.S.
(Continued from Decade VI, Vol. I, November, 1914, p. 483.) . PLATE VI.
Mempranipora supacuminata, nov. (Pl. VI, Figs. 1, 2.)
Zoarium unilaminate, always adherent.
Zoecia separated by a distinct furrow, which passes into a deep crevice at the junction points, widely rounded below but tapering very considerably and almost to a point above, with areas of the same shape aud upright rounded side walls thickening considerably below, and often developing something of an internal front wall; average length of area -28mm., breadth -2mm., but marginal zoecia often run much larger.
Owcia. No trace of any ocecium has been observed.
Avicularia vicarious, humble examples of the ‘ Lesuewri-type’, as
although strictly conformable in general structure they are only _a little larger than the surrounding zocecia; the node at which the very scanty front wall of the lower part splits into two is very inconspicuous, and the internal front wall of the upper part is relatively much wider than usual in proportion to the section of the _ area which it encloses. (I have always felt that it would be admissible to argue, on the species standing by itself, that these cells were not avicularia but ordinary zocecia with the addition of a wholly unroofed ocecial chamber; but I have never doubted myself that they were avicularia, and the recently discovered species which follows seems to put this beyond doubt.)
This species is only known to me from the base of the zone of B. mucronata at Portsdown, where it is scarce but well distributed.
‘Mempranreora Stupianpensis, noy. (Pl. VI, Figs. 3, 4.)
Zoartium unilaminate, adherent.
Zoecia piriform in outline (there being a considerable expanse of flat front wall below the area), and separated only by sutures; areas practically circular, average diameter °28 mm., but occasionally much larger ones occur.
Oecia globular, of the water-bottle type, the constriction at the neck being slight but quite distinct, with a concave free edge falling ‘somewhat back from the areal outline, small in proportion to the zocecia and with rather vague outlines, almost invariably present in the type-specimen. Beneath them the areal margin is low and very
DECADE VI.—VOL. III.—NO. III. 7
98 hk. M. Brydone—New Chalk Polyzoa.
thin, but maintains accurately the circular areal outline. This makes it impossible to confuse the base of the damaged ocecium with the internal front wall of an avicularium as the latter sets well back from the areal outline.
Avicularva vicarious, resembling very closely those of IM. subacumi- nata, but a little larger in proportion to the zocecia and with the nodal points standing out conspicuously.
I have only one specimen, from Studland, of this species; but specimens of any adherent Polyzoa are so exceedingly scarce in the Studland Chalk and the species throws such useful light on the preceding one that I have felt justified in disregarding the general objection to a species founded on a single specimen.
MemBranrrora DEMIssA, noy. (Pl. VI, Fig. 5.)
Syn. M. Britannica, var. demissa, Bryd., GEOL. MaGc., 1910, p. 77, Pl. VII, Fig. 6.
I am convinced that I was wrong in ignoring the doubts I felt at the time and treating this form as a variety of JL Britannica. Subsequent experience shows clearly that the front wall habitually developed in IL, Britannica solely as a platform for the ocecium or avicularium of the preceding zocecium never approaches in size or systematic nature that of JL demissa, while the bold sub-triangular areas of If, demissa are also quite distinctive. The specimen which I now figure—from Studland, of all unlikely places—is practically the only one I possess which shows clearly and perfectly the very fragile ocecia. There are six perfect examples in the Figure. They are merely gentle and vaguely outlined swellings, with free edges. which are marked off by a faint constriction and coincide exactly with the normal areal outline, and they form a strong contrast to those of M. Britannica, which are very bold. J. demissa first appears in rare small forms in the base of the zone of B. mucronata, but is represented, by normal forms as soon as the higher Chalk of the Isle of Wight and Studland is reached.
The same treatment should be accorded to the other form described at the same time as a variety (var. precursor) of M. Britannica, and this form must stand as a new species, I. precursor. It is now known to range down to the zone of MM. cor-testudinarium, and though upwards it ranges into the zone of B. mucronata, it does not appear to reach the Weybourne Chalk, and as UZ. Britannica does not appear to range down into the Weybourne Chalk, they never even meet. It would be interesting to know the exact range of | Reptoflustrella Meudonensis, D’Orb.,1 which looks like a relation of M. Britannica, though clearly distinguished by its avicularia.
Mempranipora Woopwarot, Bryd.,? var. PINGUESCENS, nov. CBT Vil, ie N62) This adherent form, which I know only from Trimingham, deserves. a recognition which seems properly limited to varietal. The round- ness of its areas and ocecia, the slenderness and flatness of its.
1 Pal. Terr. Crét. Franc., vol. v, p. 572, pl. 731, figs. 19-21. ? GEOL. MAG., 1910, p. 258, Pl. XXI, Figs. 1-3.
R. M. Brydone—New Chalk Polyzoa. 99
avicularia, and its general sleekness of appearance are points which effectively distinguish it from the typical and abundant free-growing form of the zones of A. quadratus and O. pilula, but are hardly of specific value, indicating rather a stage in the development of a single persistent form. To emphasize the range of evolution in this species J have added a figure of the form of the zone of If. cor-testudinarium, which is practically the earliest known.
MemBRANIPORELLA PontIFERA, nov. (PI. VI, Fig. 8.)
Zoarium unilaminate, adherent.
Zoecia slightly pyriporiform; areas oval with flattened upper end, average length *35mm., breadth -2mm.; side walls broad and bearing about six pairs of stout imperforate tubercles; in three instances in the type-specimen the area is bridged between a pair of tubercles by a broad arched bar without any lateral connexion or even suggestion of it.
Oecia only known from damaged specimens, apparently of globular type; at the point of attachment to the front wall they generally absorb part of the highest pair of tubercles.
Avicularia small, interstitial, mandibular, with a slender transverse bar occasionally preserved quite perfect.
The figured specimen is of course very imperfect, as it must be assumed that in a perfect specimen all or nearly all the pairs of tubercles would be connected by bars in every zocecium ; but it could only be by the merest chance that such a specimen would be secured, and no amount of waiting would guarantee it. ‘The species is an obvious warning against hasty diagnosis of forms that look like spiny Membranipore; but it is probably a safe rule, as the front wall elements of Membraniporella were presumably always fixed, that that genus is not in question when any of the tubercles are perforate and presumably bases of movable spines.
The species occurs very rarely in the zone of UW. cor-testudinarium ’ in Hants and the zone of If. cor-anguinum at Gravesend.
MeEMBRANIPORELLA oBscuraTa, nov. (PI. VI, Figs. 9, 10.)
Zoarvum adherent, almost always more or less multilaminate.
Zowcia very small, average length -4 mm., with heel shaped to horseshoe-shaped apertures (the outline depending a good deal on the amount of encroachment of avicularia), the lower lip of which is a straight thickened bar generally bearing a distinct median denticle ; the slightly arched front wall should be pierced by four or five pairs of radiating slits, as seen in Fig. 10, but it is only rarely that this structure can be detected, although the general aspect is so emphatically Cribrilinid that I never doubted that it would prove to belong to that family.
Owcia. No trace observed.
Avicularia small, probably mandibular, scattered in abundance along the interzocecial furrows, which they almost wholly obscure and often fill up to above the level of the zoccial front walls.
This species appears to be confined absolutely to the zone of M. cor-testudinarium, in which it is fairly common in Sussex and occurs also in Hantsand Kent. Its general indistinctness is, of course,
100 ° H. L. Hawkins—On Lovenia forbesi
partly due to its exceptional smallness and perhaps also in part to the relative intractability of the Chalk it inhabits, but it must also be due in part to secondary calcification. It is clearly one, and apparently the first, of the group which includes Jf. castrum,' Bryd., and 2. pustulosa,* Bryd. ., and which is otherwise, except for a very brief interval at the base of the zone of B. mucronata, strictly unilaminate.
EXPLANATION OF PLATE VI.
(All figures magnified 12 diams.) Fie. : 1, 2. Membranipora subacuminata. Zone of B. mucronata. Portsdown. 3. M. Studlandensis. Zone of B. mucronata. Studland. 4, M. Studlandensis. Another part of the same specimen showing broken ocecia.
5. M. demissa. Zone of B. mucronata. Studland. 6. M. Woodwardi, var. pinguescens. Trimingham. 7. M. Woodwardt. Zone of M. cor-testudinarium. Seaford. 8. Membraniporella pontifera. Zone of M. cor-anguinwm. Grea: 0. M. obscwrata. Zone of M. cor-testudinarium. Seaford.
(To be continued.)
at
If.—A REMARKABLE SrRucrure in Lovenra FORBESI FROM TILE re Miocene or Avsrratta. By H HERBERT L. HAWKINS, M.Sc., F.G.S:, Geological Department, Univer College, Reading. URING the preparation and arrangement of a series of Lovenia forbest from the Australian Miocene (presented to the Geological Department by Professor F. J. Cole), a peculiar interambulaeral structure was displayed. ‘lwo of the specimens are severely weathered, with the result that their surfaces are smooth (except for the areole of the large tubercles), while the sutures are clearly outlined in dark brown across the pale background of the plates. In this way there is revealed the surprising fact that plate-crushing and resorption, of a type similar to that often found in Echinoid ambulacra, occur in four of the interambulacral areas. There is no corresponding develop- ment in the ambulacra. iy.
As far as I am aware, this peculiar condition has not been described ‘previously in the species under notice, nor in any other Euechinoid, whether Regular or Irregular. Apart from its intrinsic interest, this apparently unique development throws much light upon the mechanism whereby the more usual ambulacral plate-crushing is produced. Hence a brief description of the specimens seems desirable ; and the description is followed by a discussion of the problem as solved by this new evidence.
The following description is based solely on the two weathered specimens referred to above. They are registered in the Paleonto- logical Collection of University College, Reading, under the numbers 546 A and B. Their dimensions (in millimetres) are as follows :—
Ant.-Post. Diam. Transverse Diam. Height. i Nash Ye ie Rtn EL 20:8 112-9 Jey 45 . 3 23:0 24-0 1. IL-2
1 GEon. Mag., 1909, p. 398, Pl. XXII, Figs. 4, 5. 2 GEOL. MAG., 1910, p. 488, Pl. XXXVI, Fig. 9.
Grou. Maa., 1916. Prats VI.
hk. M. Brydone phot. Bemrose & Sons Ltd., Collo. Chalk Polyzoa.
oars > q ft) ey \ f
ee
ey» ’
ve
from the Miocene of Australia. 101
It will be noticed that A is of a slightly different form from B, being smaller, but of greater proportional length and height. Specimen B is, in fact, rather broader and flatter than is usual for the species. On the evidence of size and tuberculation, it must be inferred that A (Text-fig. 1) is a somewhat younger individual than B (Text-fig. 2), although both specimens possess approximately the same number of plates in their tests. In both examples the ambital angle is very acute, and the adoral surface almost flat.
In each of the four paired interambulacra (areas 1, 2, 3, and 4),' the adoral surface is entirely occupied by three plates—the unpaired plate at the peristome border, and two large multitubercular plates which make a kind of plastron. Of these large paired plates, those -in columns la and 46 are crossed by a faint curved suture, seeming to indicate that they are of dual origin. Lovén (Htudes) has inferred that one or both of these plates are often double in Spatangids, but seems not to have detectedasuture in them. Thereis the appearance of a similar suture across the corresponding plates in columns 2a and 35 in specimen B, but as this occurs in that individual only it requires confirmation, and is ignored in the numbering of the plates in the succeeding description and figures.
In column la (Text-fig. 1) the plate next above the ambitus (plate 4) is narrow but complete. In column 14 there are two imperfect, lath-like plates intervening between the large ‘ plastronal’ plate (2) and the first tubercle-bearing plate of the adapical surface (5). Both of these imperfect plates take part in the interradial suture, but taper away towards the adradial suture, the adorally situated one being the shorter. As a result, plate 5 is in contact with plate 2 at the margin of ambulacrum II. In specimen B (Text-fig. 2) the condition in this column is precisely similar, but plate 3 is represented by a minute fragment extending for only a millimetre away from the interradial suture.
In column 2a, in specimen A (Text-fig. 1), plate 3 is complete, but tapers towards the ambulacrum, and is reduced to a very narrow strip at the adradial suture. In specimen B (Text-fig. 2) the corresponding plate is imperfect, disappearing at a distance of about two millimetres from the ambulacral margin. In column 26 plate 3 is complete, its height being about half that of the succeeding plates in specimen A, and about a quarter that amount in specimen B.
On: the other side of the test precisely symmetrical and similar conditions obtain. In area 5 there is nothing comparable in degree with this compression and reduction of the plates.
From the foregoing description, and particularly from the figures, it will be seen that there is developed in the interambulacra of Lovenia forbest a structure closely analogous to plate-crushing as found in the ambulacra of most Regular and many Irregular Echinoids. The only difference in character is that, whereas in ambulacral crushing the plates are usually detached from the perradial suture, here they survive at the interradial suture and fail to reach the adradial.
The plate-crushing, in so far as it produces plates homologous with demi-plates, is restricted to the two sets of interambulacral columns
1 Lovén’s notation is used throughout.
102 H. L. Hawkins—On Lovenia forbesi
bordering upon ambulacra IJ and IV. This in itself may be regarded as a piece of confirmatory evidence for the association with an ambu- lacrum of the contiguous columns of the interambulacra, as urged by Jackson (Phylogeny). The crushing occurs, to some degree, in all four of the lateral interambulacra, and even in area 5 an appreciable reduction in the height of the plates can be detected. It affects most seriously those plates that are next above the enlarged subambital plates; and is most intense in specimen B, the older of the two. In
o Its
3 Sues
TEXT-FIG. 1.—Plan of the adoral and part of the adapical surfaces of specimen A of Lovenia forbesi. x about 24. The lettering and numbering of,areas and plates,is in accordance with the method employed in Lovén’s Htudes sur les Echinoidées. The ambitus is approximately coincident with the outer margins of the plates numbered 2. All ornament is omitted.
such specialized forms as Zovenia, these plates (Nos. 2 or 2+ 3),
together with the primordial unpaired plate, become set apart early
in ontogeny for the purpose of building a strong, flat adoral surface.
There is practically no resorption cf plates at the peristome; and,
indeed, one might even regard the great increase in size of the adorally
situated plates as constituting a ‘‘ negative resorption ”’, and possibly exerting pressure upwards.
from the Miocene of Australia. 103
With these large plates stereotyped and immovable, a bar to downward movement on the part of the later formed plates is developed at or near the ambitus. It appears that in ZLovenra there is no interruption in the production of new coronal plates from the oculars (at least during a large portion of the growth: period of the individual), so that the lower (older) members of each column become jammed against the adapical margins of the large plates. This assumption
TEXT-FIG. 2.—Specimen B of Lovenia forbes: for comparison with Fig. 1. It will be noticed that the two figures are identical exceptin proportions and the degree of reduetion of the interambulacral plates at the ambitus.
receives strong support from the fact that in this species the greatest degree of compression of the plates occurs in the neighbourhood of areas IJ and IV. ‘The actual distance (measured on the curve) between the ocular plates and the adapical margins of the large adoral plates is less along those two areas than in any other part of the test, while the number of plates in each interambulacral column is the same over the whole test. Conversely, the distance from
104 H, L. Hawkins—On Lovenia forbes.
oculars I and V to the ambitus in area 5 is greater than the corre- sponding measure in any other area, and here we find but a bare indication of compression in a small reduction in the height of a few plates. A table of these measurements in the two specimens described will emphasize this point.
Number of plates in each iamb. column, 13. Distance (in mm.) from edge of ocular plates to ambitus—
Radius II. Interradius 1. Interradius 5. ALA i 15-9 16-2 19-8 Bist ‘ 16-0 16-2 19-0 Average height (in mm.) of one iamb. plate in these positions— AME tee : 1-223 C 1-246 C 1-523 B } : 1-231 C 1-246 C 1-461
(C indicates development of plate-crushing.)
In specimen B, where the distances are relatively shorter, but the normal plates actually larger, than in specimen A, the degree of plate compression is greater. In view of these conditions, it seems. impossible to resist the conclusion that simple mechanical pressure has been the prime cause of this unusual development. The growth of tubercles (to which Lambert would ascribe much influence in ambulacral plate-crushing) can have no effect in this case, for the scattered tubercles, though large for a Spatangid, are far removed from the margins of the plates and have ample room for extension.
In comparing the development of plate-crushing in this aberrant case with the similar structures in the ambulacra of many other Kchinoids, the place at which the reduced plates occur becomes an important feature. It is demonstrably at the line of junction between the unchangeable and immovable adoral plates and the less specialized movable plates higher in the column; that is, the latter plates are crushed against the barrier.
In the case of the ambulacra (and interambulacra) of the Cidaroids. there is nowhere any hindrance to the progress of the plates from apex to peristome, and no plate-crushing appears. In the other Regular Echinoids, and in the Holectypoida, the major part of the perignathic girdle is established on the ambulacral plates next to the peristome, and must, to exercise its function, remain there constantly and unchanged. At once plate-crushing appears (in the ambulacra), at the peristome margin first, extending farther up the area as specialization progresses. In Lehinocardium cordatum, as I have shown recently, an abnormal rate of plate-growth occurs in ambu- -lacrum III; but those plates of the area that are on or below the ambitus have already taken on the large, immobile character of the plates of a Spatangid adoral surface. The new plates thus crush against a barrier situated on the adapical surface, and the compound plates are restricted to the ‘petaloid’ region. In the closed petals of Clypeaster, Echinarachnius, and Laganum, a similar block occurs at the outer limit of the petal, and crushed plates make their appearance within the petals of fully-grown specimens.
The case of Zovenia under notice is a further, and even more obvious, illustration of the theory of plate-crushing in Kchinoids.
P.G.H. Boswell—Quantitative Methods in Stratigraphy. 105
that I have urged repeatedly; and the theory may be restated by way of a summary of the preceding paper.
In Loventa forbest (or any other Echinoid), persistent development of new plates from the ocular margin causes a downward (orad) gliding of the columns. If no structure is developed to interfere with this procession, the older plates become gradually resorbed at the peristome margin, or all gradually and uniformly decrease in size as they increase innumbers. If, however, some special character is assumed by a series of plates in a column (whether ambulacral or interambulacral), and this character, for reasons of function, must be maintained in a definite position in the test (e.g. the large adoral plates of the interambulacra in Zovenia or the ambulacral processes of the perignathic girdle in a Diademoid), the oncoming plates of the column become congested against the barrier thus formed. Under such circumstances the plates become lessened in height and restricted in width, forming demi-plates, and often coalescing to form compound plates. Plate-crushing is first developed, both ontogenetically and phylogenetically, at the line of contact between the moving column and the barrier.
The resulting structure may be adapted subsequently for special functions (e.g. phyllodes, ‘prehensile’ petals, or consolidation of the test fabric), but in its origin it is purely a mechanical outcome of the growth of the Echinoid test.
II].—Tae AppricaTion oF PrrroLosicaL AND QUANTITATIVE MeErHops. To STRATIGRAPHY.
By P. G. H. BosweELu, A.R.C.Se., D.I.C., F.G.S., Imperial College, London, S.W.
I. Inrropuction.
()* account of the aid it has given, paleontology has been termed
the handmaiden of stratigraphy, but up to the présent time petrology has not been called upon, so far as it might have been, to fulfil its appropriate duty towards the elucidation of the problems of stratigraphical geology and paleogeography.
The lithology of sediments has been studied very largely in the field, but is still in its qualitative stage. Systematic quantitative work has hardly been attempted. Used in conjunction with paleontology the broad study has proved of great value in determining facies, and in yielding clues to the disposition of land and water and their relative changes in past geological times. The fragments contained in the coarser rocks, such as breccias, conglomerates, greywackes, grits, etc., have been used to some extent petrologically as giving an indication of direction and distance of source, but the finer detrital minerals of sands, clays, limestones, marls, etc., have not yet been adequately studied with the same view. Our ultimate aim must be the knowledge of the exact mineral composition of every sedimentary rock in the geological column. In such a way only can the economic resources of our sediments become familiar, the exact conditions of deposit known, and the lesser features of paleogeography realized.
106 P.G.H. Boswell—Quantitative Methods in Stratigraphy.
II. Prrronogicat Meruops.
The usual petrological methods of treating sediments by panning, and the use of heavy liquids, divide samples into two important and convenient crops of densities respectively above and below a mean of about 2°8. Of the liquids in common use, bromoform, when it can be obtained, appears to be most convenient. Operations with it are clean, and, what is of great importance when hundreds of samples are being examined, very rapid, the time taken in washing with benzene, and drying, being a minimum. Its mobility is a valuable asset, but has given rise to the objection that separations are rendered less complete on account of convection currents which are set up in it by slight differences in temperature. If necessary, care can be taken to avoid these, and in the writer’s experience separation is quite as good, if not better, than with the more viscous aqueous heavy solutions, where the process takes longer and the grains move less freely. The only real objection to the use of bromoform is its loss by evaporation during separation, and while the washings (in benzene) are being concentrated. ‘Theoretically, bromoform may be used over and over again without end, but practically there is a slow and steady loss. This may be obviated to some extent by the use of separating funnels stoppered at the top, but they are usually too small to accommodate a sufficiently large quantity of sediment, the sand, etc., tends to hang round the sides, and the subsequent washing is often troublesome. An ordinary funnel fitted with a glass stopper or a rubber tube and clip leaves little to be desired; but with bromoform a large surface of liquid is exposed to evaporation. The funnel may therefore be covered by a clock glass. Mercury potassium iodide is the most suitable of aqueous solutions, crystallizing out less rapidly and being less viscous than Klein’s solution (cadmium boro-tungstate). It is very poisonous and has a corrosive action upon the skin, but these objections are not serious with clean working, for the liquid need not be touched. It should, however, be kept from air, and in contact with alittle mercury. While not as convenient as bromoform, for it is less mobile, and necessitates washing with water, and consequent loss of time in washing and drying, it is the best substitute when that liquid is procurable with difficulty (as in 1914-15). It may be quickly prepared in the laboratory from mercuric and potassium iodides, and, like other aqueous solutions, may be used and recovered repeatedly without appreciable loss. For the further separation of the heavy crop ( > 2-8) methylene iodide, of density about 3°33, is very convenient. The sediment is washed with benzene and the separation is therefore rapid. Its expense is an objection, but small quantities only need be employed for the (usually small) heavy crops.
The portion of density > 2°8 contains the heavy detrital minerals which are of greatest interest, beauty, and value from a strati- graphical point of view. Further separations may be made from this crop by electromagnetic and electrostatie methods, by the use of heavier liquids, and by hand-picking.
Apart from the included rock-fragments and compound grains, sediments exhibit considerable variation in petrology. Most of the
P.G. H. Boswell—Quantitative Methods in Stratigraphy. 107
constituent minerals are allogenic. In the authigenic group occur glauconite, hematite, limonite, marcasite, opal, chalcedony, and other forms of secondary silica, calcite, dolomite, gypsum, barytes, etc. The cementing materials of rocks come under this head, as do also those minerals such as limonite, anatase, leucoxene, secondary silica, micaceous aggregates, etc., when they result from the decomposition in situ of other minerals. It is not certain to what extent these secondary minerals are also detrital, for they may have been themselves derived as a result of previous decomposition of rocks. Anatase has been frequently observed growing upon, and at the expense of, ilmenite and leucoxene.! The opinion has been expressed that the tabular form is probably always authigenic, but that the pyramidal form may be allogenic. Among the few deposits known to the writer in which anatase is really plentiful in fairly large crystals (grains “3mm. diameter) is the Pliocene (?) sand of St. Keverne, near the Lizard, Cornwall. The sand is full of ilmenite (decomposing to leucoxene) derived from the Lizard gabbro, and there is little doubt that the blue tabular anatase is a secondary product from ilmenite. In the Yeovil sands ( Inferior Oolite) abundant yellow tablets of anatase accompany the yellow and red rutile which makes up a large part of the non-magnetic residue. Koenigsberger describes rutile pseudo- morphs after anatase in the Eastern Aar mass,? and the unexplained
abundance of rutile in many sediments indicates that much work _ remains to be done upon these isomers.
Glauconite may be detrital in certain cases. Dr. A. Morley Davies holds the view, with which the writer agrees, that the glauconite of some of the Mesozoic and Cainozoic deposits was derived from older - beds and was not formed at the same time as the sediment. In that ease redeposition probably took place under similar (i.e. reducing) conditions to those of its formation. Certainly much of the glauconite of deposits of all ages from Cambrian to Pliocene has no suggestion of foraminiferal character about the grains.
Side by side with the mineral analyses of the deposits, mechanical analyses, obtained by elutriation, should also be made. A good classification is that suggested by Mr. T. Crook: gravel 10 to 1 mm., sand 1 to -1mm., silt (or very fine sand) ‘1 to -01mm., and mud less than -01 mm. diameter. The material is, for practical purposes, sifted to |mm., and the mud or true clay portion estimated by difference in the elutriation with the form of apparatus he recommends.* If necessary, intermediate grades can be estimated and inserted later in the tables, which are not invalidated if sufficient grades had not been estimated previously. In sands (e.g. for glass-making, ete.), it is often desirable to know the percentage weights of the portions of diameter > °5 mm. and < 1 mm. (coarse sand), > °25 mm. and < ‘5mm. (medium sand), and > -1 mm. and < :25 mm. (fine sand); these can be
1 J. B. Serivenor, Min. Mag., vol. xiii, p. 348, 1908; H. H. Thomas, Q.J.G.S., vol. Ixy, p. 232, 1909; W.R. Smellie, Trans. Geol. Soc. Glasgow, vol. xiv, p. 267, 1911-12.
2 Economic Geology, vol. vii, p. 697, etc., 1912.
3 Hatch & Rastall, Sedimentary Rocks (London, 1913); Appendix by T. Crook, p. 350.
108 P.G.H. Boswell—Quantitative Methods in Stratigraphy.
obtained, if required, by treatment with circular-holed sieves, but separation below °5 mm. by sifting is hardly satisfactory.
A more detailed classification, such as the following, has then been found useful, and may be carried out with adaptations of the Schoene
apparatus. Diameter in mm.
Fine gravel , : Shes
Coarse sand : ; 4.) = fomands<"
Medium sand . F . >:265and<-5 >} Sand grade. Fine sand . > Levande < 25
Superfine sand (or coarse silt) > 05 and <1 ie
ae silt ( : : > 01 and < -05 geo Clay : : : A < O01 Mud grade.
The mud grade may be divided, if desired, into portions of diameter greater and less than -005 mm.
In sediments the portion of diameter between 1 mm. and ‘01 mm. is found to be most amenable to treatment for heavy residues; that over 1 mm. diameter frequently contains compound grains, and consists. of the lighter minerals, while that below -01 mm. diameter, being a mud grade, tends to clog the heavy liquids during separation. During deposition (as during elutriation—the reverse “process) the final velocities attained by small grains are dependent upon their surface areas (and therefore their diameters) and shape, rather than upon their densities. Nevertheless, as a result of greater density, it is found that the heavy detrital grains in any sediment often have an average diameter less than that of the lighter constituents. Minerals like mica, which have an excellent cleavage and therefore tend to occur in thin plates with a large flat surface, settle down slowly, and have, in spite of their greater density, a greater diameter than that of the accompanying quartz and felspar. Probably a constant ratio exists between the surface area (and also volume, for the thickness. probably varies with the diameter) and that of the other grains, both of light and heavy minerals. Asa result of measurement of material from various British sedimentary rocks, it is concluded that the volume of each muscovite grain is usually rather less than that of the average grain of quartz and felspar (perhaps about 80 per cent), but that the diameter of the flakes varies from two to four times that of the other heavy minerals. (The thickness of the mica flakes has been measured by focussing methods and birefringence.) The following are a few actual examples, selected from a large number :—
Diameter in mm. Other heavy detrital
Muscovite. minerals. Bunter pebble-bed, Devon (Dr. H. H. ag 5 2 to -3 Yeovil Sands F 25 -06 Lower Greensand, Hunstanton: : : : 6 25 Thanet Beds, Bramford F : : : 15 04 London Clay, Holbrook : : é : “2 -08 Claygate Beds : : : : : 15 -05 Boxstones (Crag) . : . 2 : : -5 to +6 2 Lenham Beds ‘ j , : : : “4 2
Elutriation methods depend upon the final velocities of subsidence
P.G.H. Boswell— Quantitative Methods in Stratigraphy. 109
of quartz. It is clear that each grade obtained by elutriation will contain a proportion of heavy grains which from their diameter ought to belong to a smaller grade. If the percentage of material greater than 2°8 in density were a considerable one, the method of grading would be vitiated. Apart from the occasional cases where quantities of such authigenic minerals as limonite, pyrite, and pyrrhotite, etc., are introduced (and these may be extracted early in the operations), the heavy crop reaches only 4 per cent by weight in special cases. The average found by the writer after numerous separations of rocks of all ages is about ‘6 per cent. It is often, especially in coarser sands and sandstones, much less. Fine sands consisting largely of grains *2 to ‘05mm. diameter, such as many of the samples of Bagshot Sands, appear to yield the largest residue (up to 4 per cent).” The earliest systematic work in this country on heavy detrital minerals appears to have been carried out by Allan Dick, and he was fortunate in choosing for his work Bagshot Sand from Hampstead Heath, which yields a large crop. Sands of diameter 2 to ‘5mm. (e.g. Red Crag, etc.) yield a much smaller proportion of heavy minerals.
Ili. Tue Possrprnitres anp Limrrations oF THE MerHops.
A Imowledge of the mechanical analyses of all the British incoherent sediments is economically valuable as well as of con- siderable geological importance. Our resources are not at present accurately known, but soil-analysts, authorities on water-supply and filtration, brick and pottery manufacturers, glass manufacturers, and workers in various branches of the engineering trades, particularly in the foundries, agree upon the importance of the data. From the purely geological point of view, many interesting deductions can be made regarding conditions of deposit, velocity of rivers and currents, and direction of drainage. We need, however, much more experi- * mental work like that inaugurated in this country by Forbes, Sorby, and others, and carried on abroad, particularly in Germany and the United States,> in properly equipped laboratories. The experimental work is largely synthetic, and seeks to build up deposits under certain known conditions; the corresponding analytical work upon geological deposits has rather tended to lag behind the synthetic—a result not expected in petrology. When sufficient data have accumulated it should be possible to devise schemes for graphical representation of sedimentary rocks, similar to those in use for igneous rocks. Diagrams might be used upon maps, and being placed at certain points over an outcrop, yield at a glance information as to heteropic or isopic formations, lithological changes, presence of shore-lines, etc.
But not only should deposits actually mapped at the surface be so treated. Specimens from wells, water- and trial-borings should be carefully preserved and subjected to analysis. It is a matter of
' R. H. Richards, Ore-Dressing, 1906, tables in Appendix.
2 Exclusive of such local sands, etc., such as those bordering the granite masses of Devon and Cornwall. These sands may be full of tourmaline, etc.
® See, for example, the recently published Professional Paper 86, U.S.G.S., ‘‘The Transportation of Débris by Running Water ’’ (G. K. Gilbert).
110 P.G.H. boswell—Quantitative Methods in Stratigraphy.
great regret that tens of thousands of borings should have been made and so little of the material met with preserved. For mechanical analyses only 10 to 20 grams of the deposit are required, and for mineral analyses about a kilogram. It is to be hoped that this work will be developed in future. The drawing of sub-formational contour-lines has already proved of great value in water-supply questions, and in work upon concealed coalfields.' Combined with the isopachytes (lines joining points of equal thickness*) of super- imposed beds, these contour-lines yield valuable information as to the date and trend of folds and faults and the extension of deposits under- ground. But it is also necessary to know the lithological variations of the buried strata, and if contour-like grade-lines are also to be plotted upon maps, and compared with isopachytes and sub- formational contours, our basis of work on underground deposits must be quantitative. If from the graphical representation of sediments (preferably from curves) we can devise a scheme which represents by a number the average mechanical composition of a rock, we shall, by plotting these numbers referring to ‘ grades’ upon a map, and drawing ‘contour-lines’, possess a valuable method of indication, not only of thicknesses of beds (by isopachytes), and of the form of the surfaces of concealed beds (by contours referred to Ordnance datum), but also of changes in lithology, the proximity of axes of unrest, etc., in rocks now buried deeply. Such information cannot fail to be of considerable economical value, and its academic interest is as great. In questions of water-supply much time and money will be saved if the thicknesses and exact mechanical composition (and therefore the permeability and filtering value) of the various members of the overburden with respect to the water-bearing stratum are known.?
Not only the mechanical composition, but the mineral constitution also, of each bed occurring in a boring, should be worked out. Evidence of unconformity between rock-series is thus accentuated and may be of value where fossil evidence is lacking or the relations of the beds obscure in the small core of the boring. It may be serviceable in certain areas, for example, to regard the change of mineral composition which usually exists, as the dividing line between the Permian and Triassic systems. The proximity of masses of crystalline rocks, of igneous bosses, etc., or even areas of ancient sediments forming old land-areas, may be revealed from borings as a result of the study of detrital minerals of the sediments bordering such land-areas. Additional information may be gained regarding
1 Since the above was written Professor W. G. Fearnsides has read a paper before the British Association upon the Underground Contours of the Barnsley Seam (GEOL. MAG., October, 1915, p. 465). See also ‘‘ The Use of Thickness Contours in the Valuation of Lenticular Coal Beds’’ (G. S. Rogers and C. E. Lesher) : Heon. Geology, vol. ix, p. 707, 1914.
2 Professor E. Hull used the term isodiametric (or isometric) lines, as those joining points of equal thickness of a formation before denudation had acted upon it. See Q.J.G.S., vol. xviii, p. 127, 1862.
* C. S. Slichter, ‘‘ Motions of Underground Water’’?: Water Supply and Irrigation Papers, No. 62, U.S.G.S. Hazen’s ‘ Uniformity Coefficient’ obtained by sifting is not satisfactory, and is applicable only to coarse deposits.
kt. M. Deeley—The Thames Valley Gravels. LE
the position and extent of old shore-lines, and in the development of concealed coalfields, especially on outer ground where borings are as yet scarce, indications of the possible projection of pre-Carboniferous rock masses through the workable measures must be of great value. The information obtained by a petrological study of the sediments will thus be combined with that resulting from work on the mechanical composition, and with. the analysis of records of borings and their cartographical expression in the form of isopachyte systems and sub- surface contours. If the results obtained actually fall short of the above ideal, the method will still be justified. A few years ago Professor W. W. Watts wrote in his suggestive Presidential Address to the Geological Society (1911): ‘In order to obtain what Dr. Marr has called the ‘ geogram’ of a formation in its greatest perfection, we require to know the entire extent of its variations, not only along its outcrop, but in that part which is hidden from sight.’”? The whole of the section ought to be quoted, if space permitted, in this connexion. The methods of work detailed above help considerably towards the perfect conception of the ‘ geogram’ of a formation.
(To be continued.)
TV.—Tue Frovrio-cracta, Gravets or tHE THames VALLEY. By R. M. DEELEY, M.Inst.C.H., F.G.S. (Concluded from the February Number, p. 64.)
T about 55 miles we reach the Hendon Lobe fan. At Dollis Hill the base of the fluvio-glacial beds lies at a height of about 200 feet, whilst their upper limit at Hendon is about 280 feet. On Finchley Hill to the north-east the Boulder-clay lies between the levels of 240 and 340 feet. This was a small lobe, and the fluvio-glacial fan may have sloped rapidly towards the fluvio-glacial gravels of the main stream. On the section, Fig. 2, the heights are shown without _ correction for slope towards the River Thames.
Where the Lea and Roding Valleys join the Thames Valley, and to the east as far as Hornchurch, the ice reached the fluvio-glacial gravels of the Thames. West of Woodford, at 43 miles, gravel caps the watershed between the Lea and Roding. Here the height of the deposit varies from 200 to 210 feet.
That the Boulder-clay should occur here as low as 80 feet above O.D. is very interesting, for it shows that, as at St. Albans, the fluvio-glacial gravels must have been piled against the ice face and buried its end in places. Indeed, as the lower Thames is reached the evidence favours the assumption that in pre-Chalky Boulder-clay time the valley was perhaps within about 80 feet of its present depth, and was subsequently filled with a deep mass of fluvio-glacial gravel, a view, as previously stated, held by Pocock.
At Dartford Heath, 22 miles, the gravel is from 90 to 140 feet above O.D. The upper portion of this deposit locks like a schotter formed by braided streams ; but the lower portion is a clean current- bedded gravel and sand, such as an ordinary river might form.
The fossiliferous gravel at Greenhithe and Swanscombe, like the Dartford Heath deposit, lies within the upper and lower limits of
112 R. M. Deeley—The Thames Valley Gravels.
the fluvio-glacial gravels; but the exact relationship of the deposits to the fluvio-glacial gravels is uncertain. It is about 28 miles from the eastern edge of the Map, Pl. LV, Fig. 1.
The gravel at High Halston, 18 miles, is a deposit which is from 100 to 200 feet high, and may belong to this series of gravels. ‘The highest outlier at the Telegraph Station, which is still more elevated, cannot belong to the series of gravels we are considering.
Leigh, at 15 miles, shows gravel from about 150 to 160 feet Prera O-D.; “whilst the Southend ‘eravel is from 100 to 160 feet. From the neighbourhood of Southend the gravels run in the direction of Sales Point at the mouth of the Blackwater River. In this stretch the gravel of the main stream seems to have been joined by a fluvio- glacial fan coming from the direction of Billericay, where it is from 220 to 240 feet above O.D. — Its distance from the fluvio-glacial gravel of the old Thames is about 16 miles, and allowing 5 feet per mile fall we get 14) to 160 feet as the height of the gravel of the main stream.
Southminster stands on an outlier of gravel which varies from 50 to 80 feet above O.D., and this place is opposite the point where the centre line of the old Thames Valley reaches the east side of the Map, Pl. IV, Fig. 1.
All the gravels of the Tilehurst Terrace do not contain erratics derived from the glacial drifts: On the south side of the River Thames Bunter pebbles are absent, except towards the east. Portions of the gravel to the south and west were formed by the local drainage, whereas the portions to the north side of the river were largely formed by the drainage from the ice margin, the deposit becoming a more and more mixed one as it is followed to the east.
The slope of the Tilehurst Terrace deposits from the Goring Gap to the east does not appear to have been by any means a regular one ; but whether the irregularity is wholly due to the varying amount of water and sediment coming down from the various ice lobes or to the subsequent warping of the district is not clear. Perhaps the debris was poured into the Thames Valley by the St. Albans Ice Lobe in such quantities that it collected here in unusual thickness in the neighbourhood of the confluence of the Colne and Thames.
At Southend the High-level Terrace Gravels wrap the slopes. in avery peculiar manner. Indeed, it would appear that the present estuarine portion of the Thames ‘Valley in pre-Chalky Boulder-clay time continued to slope to lower levels in a north-easterly direction, and that in Chalky Boulder-clay time the valley was deeply filled with fluvio-glacial gravels which have since been re-excavated, leaving traces of the High-level Gravel Terrace deposits at all heights from sea-level up to 130 feet or more.
This filling up of the valley with glacial detritus in its lower reaches may have been due to the ereat quantities of material thrown into the valley by the Lea Valley Lobe and the ice lobes which debouched into the valley from the rivers of Suffolk and. Essex.
During the time the Chalky Boulder-clay was being laid down the Tertiary and Cretaceous rocks extended some distance in a north- easterly direction into the North Sea, being probably continuous with those of France. Since this time subaerial denudation and coast
R. M. Deeley—The Thames Valley Gravels. = 1138
erosion have removed this easterly watershed of the Thames and given it its present direction of outlet to the sea. Probably the initiation of the Straits of Dover dates from the advent of the first ice-sheet which crossed the North Sea to Britain, and if the Straits existed in Chalky Boulder-clay time they were probably very narrow. Indeed, the reason why the early ice-sheets of the Pleistocene period . were able to cross the North Sea was the absence there of the volumes of warm water which now pass from the south through the Straits. The erratics in the raised beach of the south coast of England probably reached their present positions at a later period; for there is much evidence which favours the view that the last cold period occurred long after the Tilehurst Terrace Gravels were laid down.
It may be that the Tilehurst fluvio-glacial aeatels did not at any one time quite fill the valley between the heights shown by the line BB and CC, Fig. 2; but rather that terraces of very considerable thickness were formed between these limits, for the grading and aggrading of the valley varied in accordance with the varying quantities of material thrown into it from time to time by the glacier streams.
Some of the gravels which stand at a higher level than those of the High Terrace remain to be noticed. Monckton } describes some gravels which rest on the Ashley and Bowsey Hills. He considers that some of the pebbles found in them point to a glacial origin. Mr. White found a pebble of grey chert with casts of detached joints of erinoids at Bowsey Hill and another of similar character at Ashley Hill. Both the black and grey cherts found may well have been derived from the Carboniferous Series to the north. These gravels also contain a great abundance of white quartz pebbles. On the north side of the Thames, opposite the Bowsey and Ashley Hills, there are also gravels at a similar height, and as shown on the Map, Fig. 1, higher-level gravels run along the south-eastern slopes of the Chiltern Hills, above the fluvio-glacial deposits of the St. Albans Ice Lobe. They also form a well-marked terrace resting on a platform about 400 feet high in the Kennet Valley and on the high land to the north-west of Bagshot. Here, however, they do not contain Northern Drift. Their extent and boundaries are very uncertain and the method of their formation is obscure. The Bowsey and Ashley Hill gravels. are shown thus + in the diagram, Fig. 2. They seem to be - much too high to have been formed when the St. Albans Ice Lobe was in existence. Some of the plateau gravels lower down the Thames may also be of the age of the Higher Terrace Gravels.
A possible explanation of the existence of such high-level gravels containing Northern Drift erratics may be as follows The position of the Thames Basin is a very interesting one from the point of view of stratigraphical glacialogy ; for its southern, central, south-western, and western portions were outside the area occupied by the ice-sheet which advanced to some extent over the northern and north-eastern watershed ; and owing to its position on the edge of the ice-sheet, it felt the full effect of any variations in the position of the ice margin.
1 Q.J.G.S., vol. xlix, p. 314, 1893. DECADE VI.—VOL. III.—NO. III. 8
114 Rh. M. Deeley—The Thames Valley Gravels.
Before we can consider the question of the high-level gravels of the Thames Valley as being in any way properly dealt with, it is necessary to get as clear a view as possible of the movements of the ice-sheets which invaded this area. This is a difficult matter to accomplish, for British geologists have generally confined themselves to considering the greatest area which can be shown to have been covered by ice and the directions in which it probably travelled ; but. the trend of the rock striz and the variable nature of the deposits in some areas show that the direction of the flow changed very con- siderably from time to time, as also did the areas covered by the ice at different times during what seems to have been the same epoch of glaciation.
One of the most interesting ice-flows is that which passed over the Stainmoor Pass and carried with it the well-known Shap granite. That at one time this ice-flow passed in an easterly direction out into the North Sea is shown by the occurrence of this rock at Elwick, as far north as Hartlepool. This uninterrupted movement of the Stainmoor ice to the east was also shared by that coming through the Tyne Gap.’ Trechmann shows that the ice from Scandinavia pressed against the English coast between these two lobes. Subsequently the ice from the Cheviots was deflected in a southerly direction by this North Sea ice and passed down the coast. It has generally been considered that this deflection of the British ice-flows was only due to the advancing Scandinavian ice, but it may have been partly due to the waning of the British ice-sheets as the Scandinavian ice advanced and thickened.
Lamplugh*? shows that further south at Flamborough Head similar changes in the direction of the flow took place, the Basement. Clay of Holderness being the oldest and having a Scandinavian origin, whilst the subsequent flow was down the coast. This alteration in the direction of the ice-flow becomes more marked as we reach Central and Western England. In the Trent Valley this change in the direction of ice-flow is very pronounced. Deeley * has shown that in this area the ice first came from the west, and that its fluvio-glacial gravels and sands went as far east as Grantham. Subsequently this ice-flow melted away and its place was taken by the ‘‘ Northern ”’ ice-flow which laid down the Chalky Boulder-clay. One lobe of this. flow turned towards the west and passed up the Trent Valley, laying down upon the older boulder-clays and fluvio-glacial deposits the Chalky Boulder-clay and its fluvio-glacial deposits. The ice from the west and that which came down the Derwent Valley advanced into a submerged country, a submergence probably due to the presence of the Scandinavian and Scotch ice in the North Sea. Associated with the hard till with glaciated boulders formed by the early western and Pennine ice, are clean current-bedded sands and eravels not containing flints, and sedimentary clays containing well- glaciated boulders, but no flint.
That this ice-sheet was very thick in the Irish Sea is shown by the
1 Q.J.G.S., vol. lxxi, pp. 538-80, 1915.
2 Q.J.G.S., vol. xlvii, pp. 384-429, 1891. 3 Q.J.G.S., vol. xlii, pp. 437-79, 1886.
R. M. Deeley—The Thames Valley Gravels. 115
fact that one lobe of it passed over the gap in the Pennines near Buxton and distributed Scotch and Cumberland rocks on the high land above Tideswell. At Bakewell, well up the Derwent Valley, there is a good deposit of boulder-clay formed by this ice. The graye-yard stands on it, and heaps of foreign erratics ure to be seen there. Another thick deposit of it is to be seen at Crich, where it rests upon a well-glaciated floor of Carboniferous Limestone. So thick was this ice in the Irish Sea, that it completely submerged Snaefell in the Isle of Man, which is 2,034 feet high. Coming from Cumberland and Scotland one lobe of it passed to the east of Wales into the Severn Valley. Here, reinforced by ice from Wales, it pressed against the Cotswold Hills, forming gravels and leaving Northern: Drift pebbles on their flanks, such as Millstone Grits and quartzite pebbles, but no flints. Such pebblesand gravels have been found, according to Lucy,’ at heights of 750 feet above the sea-level. If the ice reached such a thickness there must have been an overflow of water into the Thames Valley through the Andoversford Gap to the east of Cheltenham. Such thick ice would also pass over the Thames watershed into the Evenlode and Cherwell Valleys, and in this way Northern Drift found its way into the upper Thames Valley, where it is now found at heights considerably above the Tilehurst Terrace Gravels. As far as the British ice is concerned this would appear to have been the time of its greatest extension. However, the succession of events which preceded the advent of the Chalky Boulder-clay ice may have been much more complex than is here indicated. There is very little evidence of this in the area we are considering; but in Norfolk, Suffolk, and Northern Essex the complexity of the Drifts is very striking.
Upon the westerly drifts of the Trent Basin there rest the Great Chalky Boulder-clay and its associated gravels and sands. It is clear from the arrangement of the deposits that, before the North Sea ice ‘advanced up the Trent Valley, the Irish Sea ice had retreated a considerable distance. Whether in the Trent Valley to the west of Burton-on-Trent the eastern ice coalesced with that coming from the west is uncertain. Lucystates that along the flanks of the Cotswolds, and running up to the Marlstone Terrace to heights of about 610 feet, there is a line of gravel containing an abundance of chalk flints. Therefore, although the British ice may have been reinforced at this time by the ice which formed the Chalky Boulder-clay, its gravels only reach heights of 610 feet, whereas the earlier British ice formed gravels at heights of 750 feet.
That the Chalky Boulder-clay glacier reached the upper.end of the Evenlode Valley is clear; for Lucy states that at Paxford, 34 miles north-west of Moreton-in-the-Marsh, he saw in a field which was being drained fully five feet of boulder-clay, containing some flints, quartzose pebbles, Lias, greenstone, Millstone Grit, and syenite from Charnwood. At Little Wolford, about 8 miles east of Moreton-in-the- Marsh, in a gravel-pit, were found pebbles of a hard red species of chalk which occurs not infrequently in the Wolds of Yorkshire and
1 The gravels of the Severn, Avon, and Eyenlode, and their extension on the Cotswold Hills.
116 R. M. Deeley—The Thames Valley Gravels.
Lincolnshire. Buckland, many years before, had recognized this red chalk. Another lobe of the Chalky Boulder-clay glacier moved up the Ouse Valley and reached the limits shown in the Map, Fig. lL.
If the above reading of the teaching of the boulder-clays, sands, and gravels be correct, then the first erratics to reach the Thames Basin were brought into the district by the British ice-sheet which reached the more northern and western portions of the Thames Basin, but may not have reached the Ouse Valley or the Lower Thames Valley.
It has been maintained by Tutkowski’ and others that near the margins of great ice-sheets cold and dry conditions prevail. Outside this dry area the climate, although cold, is much more moist, and the precipitation very considerable. It may be that some of the moisture which does not fall near the ice margin is precipitated on the ice some distance from its edge owing to local winds. To some extent this reduced precipitation at the ice margin is a feature of the Antarctic Continent, for Bouvet Island, although small and out in the open ocean, is completely covered with ice down to the water’s edge, whereas the coast of the continent, hundreds of miles to the south, is not ice mantled to the same extent.
It is possible that Great Britain, before the Scandinavian ice first reached it, was outside the dry zone and, like Bouvet Island, snifered intense glaciation, but that as the Scandinavian ice advanced over the North Sea floor towards Britain the dry zone advanced with it, and that when the continental ice-sheet reached our shores the air had become so dry that the local British ice-sheet, partly or wholly, melted away. ‘That such a dry period existed is shown by the discovery of dreikanters* in the Midland Counties.
_ As far as can be made out, all the boulder-clays we have considered seem to belong to one cold period,® but this is by no means certain.
It may be that the Bowsey and Ashley Hill gravels and some others to the north-east along the edge of the Chiltern Hills, in the Kennet Valley, and to the north-west of Bagshot, may have been formed by the early outflow water of the British ice-sheet ; but that the Thames, as suggested by Sherlock and Noble,‘ then ran past St. Albans in a north-easterly direction scarcely seems probable, nor is it likely that it passed into the Ouse Valley near Buckingham, as suggested by Harmer.
Sherlock & Noble® also suggest that the Clay-with-Flints is a glacial deposit, ie. a boulder-clay. Now, according to the evidence we have, the Clay-with-Flints occurs on those portions of the Chalk escarpment which was never overridden by the Chalky Boulder-clay ice-sheet, and does not occur on those portions which have been overridden. There is a marked difference between the Chalk escarp- ment to the south-west of Luton as compared with that to the north- east. Sherlock & Noble remark that ‘‘an ice-sheet coming from the
1 Scot. Geol. Mag., March, 1900.
2 Matley, Q.J.G.S., vol. Ixviii, p. 293, 1912. 3 Q.J.G.S., vol. xlii, pp. 439 and 466, 1886. 4 Q.J.G.S., vol. lxviii, p. 206, 1912.
® Tbid., p. 199.
R. M. Deeley—The Thames Valley Gravels. EG
north and north-west would sweep up these materials and produce a confused mass known as Clay-with-Flints”. But from the distribution of the boulder-clay and gravels the ice appears to have come from the north-east. Deep snow on the Chilterns may have modified the deposit. The Clay-with-Flints seems to be such a deposit as we may expect to find filling up surface channels formed by the subsidence of the chalk into underground channels resulting from the solvent action of water, or filling swallow-holes. As the Tertiary beds were removed they would supply material to fill up such hollows as they formed. The brick-earths thus produced rest upon a layer of clay and flints which seems to be a chalk residue. Sarsen-stones were once very probably distributed over the whole area, and where they rested upon the surface they were removed for building purposes centuries ago, or destroyed by atmospheric agencies. They are now only to be found where they were buried.
At Sonning, Smith & Dewey’ give the height of the Boyn Terrace as 180 feet, and with this deposit they correlate the Dartford and Swanscombe Terraces. As the Tilehurst Terrace is at a height of 275 feet at Sonning, the Boyn Terrace? is thus 95 feet lower. Both at Dartford and Swanscombe the gravels lie well within the limits of the Tilehurst Terrace Gravels. They must, therefore, have been formed either before the Tilehurst Gravels were laid down or whilst the River Thames was re-excavating its valley through the fluvio- glacial deposits.
Very few remains have been found in gravels on a level with the Tilehurst Terrace Gravels except to the south of the Thames on the east and west sides of the Darent River. Here at Dartford and Swanscombe mammalian and other remains have been found in considerable numbers. Much further work will have to be done before the age of these mammaliferous gravels can be said to have been settled. The remains they contain seem to show that there is a wide gap between them and the Taplow or Middle Terrace deposits. On this point Hinton® says, ‘‘ Excepting the elephant, rhinoceros, Felis, and possibly two of the deer, all the forms mentioned. differ from those whose remains are found in the earliest deposits of the next or Middle Terrace of the Thames Valley at Grays, and they approach those occurring in the ‘ Forest Bed’ series and the Upper Val d’Arno Pliocene.” It is possible that the Dartford and Swanscombe Gravels are in part, at least, older than the fluvio-glacial gravels, for Leach * found in the lower portion of the Dartford Heath Gravel mammalian remains of beasts which it is unlikely lived when the upper portion of the gravel bed was deposited by a river fed by streams coming from an adjacent ice margin.
1} Arche@ologia, vol. xiv, p. 178.
2 The Geology of the Country around Windsor and Chertsey (Mem. Geol. Surv.), p. 67.
3 Proc. Geol. Assoc., vol. xxi, p. 492, 1909-10.
4 Proc. Geol. Assoc., vol. xxiv, p. 340.
118 F. R. C. Reed—On the genus Trinucleus.
V.—Sepewicx Museum Nores. Nores on tHE GENUS Z'RrINUCLEUS. Part LY.
By F. R. Cowper REED, Sc.D., F.G.S.
Tur Gunat AREAS.
(J\HE triangular non-perforated areas lying on each side of the
glabella and bounded in front and laterally by the fringe are usually described as the cheeks and distinct from the fringe, as if they alone corresponded to the fixed cheeks of the Opisthoparia and Proparia, or even included also the free cheeks of these orders. But if the facial suture is marginal, and if the lower plate of the fringe is considered to represent the free-cheeks, as Beecher’ maintained, the upper plate of the fringe must be regarded as merely a modified marginal portion of the fixed cheeks, so that the triangular areas within the fringe would only constitute the inner part of the fixed cheeks.
Whether we regard this view of the homologies of these structures as correct or not (see below), we must note that there is sometimes no sharp demarcation of the fringe from the so-called cheeks, scattered pits (particularly near the genal angles) occurring within the generally regular inner limits of the fringe, as for instance in T. concentricus of the Onny River (Guot. Mae., Dec. V, Vol. IX, p. 349, Pl. XVIII, Fig. 4, 1912).
It is, however, convenient to describe these so-called cheeks apart from the fringe, the characters of which have been discussed on a previous occasion (op. cit.), and we may accordingly term them the genal areas to avoid confusion and premature conclusions.
There are three more or less distinct types of genal areas recognizable amongst the species of Zrinucleus, 1.e. :
1. Genal areas divided into two more or less unequal portions by
an oblique ridge or line of bending, each portion having a different surface ornamentation, ro a Murchisont, T. Gibbsi, T. Htheridger.
2. Genal areas marked with a horizontal or slightly oblique line (‘‘ocular ridge” or ‘‘line’’) running outwards from: the side of the glabella to a median or submedian tubercle (‘‘eye’”’ or ‘‘ocular tubercle’’) and sometimes beyond it. The ornamentation of the surface is uniform. E.g. 7. setv- cornis, T. Bucklandt.
3. Genal areas without any ridge or line, uniformly convex, without ‘‘ocular tubercle”. ‘The ornamentation of the surface is uniform. E.g. 7. concentricus.
These three types may now be described in detail, and their
development and relations studied in various species.
1. In Z. Murchisoni, Salter (see Grou. Mac., Dec. VI, Vol. I, p. 352, Pl. XXVIII, Figs. 4, 4a, 1914), a narrow semilunar area stretches along the inside of the fringe from the pseudo-antennary pits at the front end of the glabella to “the postero-lateral outer angle of the genal area, and is marked off from the rest of the genal area
1 Beecher, Amer. Journ. Sci., ser. IV, vol. iii, pp. 100, 103, 183, 186, 1897.
F. R. 0. Reed—On the genus Trinucleus. 119
by a nearly straight oblique line along which the surface is bent or angulated. The semilunar outer band thus formed slopes down more or less steeply to the fringe, and is differentiated from the rest of the genal area. The line of angulation is marked at its posterior end by a short ridge forming its crest, beyond which lies a deep pit in the pleuro-occipital furrow. Salter’ considered that this line of angu- lation occupied the place of the facial suture of other trilobites.
The semilunar outer band is smooth in the species 7. Murchisont, but the whole of the inner portion (with the exception of a narrow region alongside the basal part of the glabella) is covered with a coarse reticulation of fine raised lines which arise as a fan-like group of thicker lines radiating from a small notch behind a tubercle projecting into the axial furrow at the level of the first lateral furrow of the glabella. These radiating lines rapidly break up into the general reticulation of the surface, so that the radial arrangement is almost lost. The pseudo-frontal lobe of the glabella, which possesses a median tubercle, has similar fine reticulation, but anteriorly the meshes are elongated transversely so as to be roughly concentric to the front end; posteriorly they became hexagonal or polygonal lke those on the genal areas. The small inner portion of the genal area on each side of the base of the glabella is only minutely granulated, which is significant (see below).
In Z. Gibbst, Salter, and 7. Etheridge, Hicks, the angulation of the genal areas and differentiation into two portions exhibit the same general characters. But in the former species the angulation is sharper and the outer band narrower, and the fan-like arrangement of the reticulating lines on the posterior part is not so clear.
In 7. Htheridgei the genal areas are divided into two nearly equal parts by the angulation, but itis less sharply marked and often nearly obsolete. The different superficial characters of the two parts are, nevertheless, retained. No definite point of origin for the reticulations ‘ean be recognized in this species, a general honeycomb-like meshwork existing all over the inner region with the exception of the inner posterior angle alongside the base of the glabella, which is smooth. A median tubercle is usually visible on the pseudo-frontal lobe of the glabella. In none of these three species is there a definite ocular ridge or ocular tubercle on the genal areas.
It appears probable that we may correctly compare the radiating and reticulating lines on the surface of the genal areas with the so-called nervures or veins on the cheeks of Dionide (although their radiating arrangement is better preserved in the latter genus), for they arise from the same point on the axial furrows. Similar structures having an identical origin are found in the cheeks of many Cambrian genera, which are devoid of compound eyes, e.g. Hrinnys, LElyx, Liocephalus, and other members of the Conocoryphide.
Beecher regarded the meshwork and lines as belonging to the nervous system, but Lindstrém? considered them as ramifications of the circulatory system, the larger lines being the main vessels and
1 Salter, Mem. Geol. Surv., vol. iii, 2nd ed., p. 516, 1881.
2 Lindstrém, Kongl. Svensk. Vet. Akad. Handl., Bd. xxxiv, No. 8, pp. 18-20, 31-3.
120 F. R. C, Reed—On the genus Trinucleus.
the smaller ones representing capillaries and venules as suggested by the genus Limulus. It can hardly be doubted that the general reticulation of the surface is not merely a superficial ornamentation of the shell of no functional importance, particularly when we are able to trace its direct connexion with a definite group of radiating vessels always arising from the same spot on the axial furrows.
The small smooth or ciierenly, ornamented regions close to the base of the glabella suggest the ‘alar areas’ of Harpes and Dionide, which are also traceable in some species of Ampyax and are found clearly developed in larval stages of TZrinucleus as Beecher’ demonstrated.
The nature and history of the semilunar outer band in front of the angulated line crossing the genal areas is intimately bound up with the whole interpretation of the structure of the head-shield of the genus. But before discussing this vexed question it will be best to describe the characters of the two other groups into which I have divided the species according to their genal features.
It may, however, be naturally expected that in the earliest representatives of the genus which are comprised in my first group, and are confined to the Arenig and Llandeilo Beds, we should find the evidence of its affinities and original structure. Later species in the stratigraphical succession would be expected to diverge more — from the primitive stock and to have suffered additional modification.
There is a link connecting the first group with the second, and it is found in the species Z. fimbriatus, Murchison, the position of which is intermediate. For it has no division of the genal areas into two parts by a line of angulation, their surface being gently and uniformly convex; there is no ocular tubercle and no typical ocular ridge, though Salter? and McCoy.* put this species in the genus Zretaspis, which is characterized by their possession. The diagonal facial suture which McCoy‘ clearly represented in his figure does not exist. There is, however, a small tubercle in young individuals® situated in - the axial furrow opposite the first lateral furrow of the glabella, just as in 7. Murchisont, but there is no such definite group of nervures
radiating from it. over the genal area. We may, however, observe that near the posterior lateral angles of the genal areas the inter- lacing sinuous lines, which form the reticulations on the surface, converge and are grouped together to form larger, more elongated meshes directed towards a small tubercle near the posterior border with a pit in the pleuro-occipital furrow, asin 7. Murchisoni. The inner posterior angles are also nearly smooth with pees faint or obsolete reticulations, thus affording traces of the ‘alar areas’ The rest of the genal areas is covered with a polygonal or hexa- gonal fine meshwork. ;
The French species 7. Bureaut, Oehlert,* which seems to belong
1 Beecher, Amer. Journ. Sci., ser. 111, vol. xlix, pl. iii, figs. 1, 2, 1895.
®? Salter, Dec. Geol. Surv., vii, pl. vii, fig. 8, 1853.
* McCoy, Syn. Brit. Pal. Foss. Woodw. Mus., p. 146.
* Ibid., pl. in, figs. 16, 16a.
° Reed, GEOL. MAG., Dec. VI, Vol. I, Pl. XXVIII, Fig. 3, 1914.
® Oehlert, Bull. Soc. géol. France, ser. WI, vol. xxiii, p. 308, pl. i, fig. 7, 1895.
F. R. C. Reed—On the genus Trinucleus. 121
here, is of interest from possessing two well-developed raised nervures on the genal areas, starting from a point on the axial furrow alongside the pseudo-frontal lobe, and then diverging as they cross the genal areas to converge and unite a little in front of the posterior lateral angle. These structures are undoubtedly of the same nature as those described in 7. Murchisont and 7. fimbriatus, having the same point of origin, same general course, and same point of termination; and they bear a specially close resemblance to the nervures on the cheeks of Dionide Lapworth, Etheridge, jun., and Nicholson,’ from the Whitehouse Group of the Girvan district. The rest of the genal surface of 7. Bureau is said to be smooth or minutely punctate, and no reticulating lines are described. Ocular tubercles are absent.
2. We pass now to consider the typical members of the second group in which a definite ocular ridge and ocular tubercle is developed in each genal area. These structures find their expression in most of the members of McCoy’s genus Zretaspis. The ocular ridge starts at the level of and opposite the first lateral furrow of the glabella, and thus corresponds in place of origin with the marginal tubercle and commencement of the radiating lines in Z. Murchisoni and its. allies. Usually the ridge ends in a small tubercle called the ocellus or ocular tubercle by most authors, and it may run out at right angles to the axial furrows or be directed rather obliquely backwards towards the postero-lateral angle. It is occasionally continued beyond the ocular tubercle to this point with diminished strength, as may be seen in the smaller specimens from Thraive Glen, Girvan, which are attributed to 7. Bucklandi, Barr. In these this extension of the ridge ends against the fringe a little in front of the postero- lateral angle of the genal area. Nicholson & Etheridge, jun.,” noticed and described this feature in this Scotch species, and the present author * has also described it in 7. subradiatus from the same area. Ruedemann‘ has observed its occurrence also in JZ. reticulatus, Ruedemann. The inner and outer portions of the ocular ridge do not correspond in position or course with the line of bending which crosses the genal areas in the first group; but as above pointed out the point of origin of the ocular ridge coincides with that of the group of nervures. ©
Not only may the outer portion or extension of the ocular ridge disappear, as is the case in the large form of 7. Bucklandi from Girvan, but the inner portion between the axial furrow and ocular tubercle may likewise become obsolete, leaving the latter isolated. Since the young of 7. concentricus (Eaton) possesses an ocular ridge (but not its extension) as well as an ocular tubercle, according to Beecher,*® both structures have been held to be phylogenetically primitive characters; and if this is sothe loss of the outer and inner
1 Reed, Girvan Trilobites (Paleont. Soc.); pt. i, p. 25, pl. iv, fig. i, 1903.
* Nicholson & Etheridge, Mon. Silur. Foss. Girvan, fase. 2, p. 191, 1880.
3 Reed, Girvan Trilobites, pt. i, p. 12, pl. ii, figs. 1-6, 1903.
4 Ruedemann, Bull. 49 New York State Museum (1901), Paleont. Papers 2, p. 41, pl. iii, figs. 11, 15-20.
° Beecher, Amer. Journ. Sci., vol. xlix, p. 309, pl. iii, 1895.
122 F. R. C. Reed—On the genus Trinucleus.
portions of the ocular ridge mark a more advanced stage in develop- ment. To this question we will return later. With regard to the function of this structure Beecher (op. cit.) remarked that “from the direction of the optic nerve in Zimulus and its relations to the surface features of the cephalothorax, the eye-line [ = ocular ridge! probably represents the course of that nerve”. The Bohemian examples of 7. Bucklandt, according to Barrande, do not possess an ocular ridge, the ocellus being isolated on the genal area.
It may be suggested that the ocular ridge in this Group 2 with its outward extension represents a specialized and concentrated nerve- supply and corresponds to a specially enlarged nervure of the diffuse radiating bundle of nervures in Group 1. Its presence is probably correlated with that of the ocelli; and the absence of visual organs in Group 1 seems to be connected with the breaking up and irregular extension of the nerves over the whole surface, since we find a similar condition in many blind Conocoryphide. Inthe large Girvan examples of Z. Bucklandi in which the ocular ridge is obsolete the reticulating lines which cover the genal areas with a polygonal meshwork start as radiating or sinuous nervures from the same point on the axial furrows as the ocular ridge and as the corresponding nervures in Group 1. ‘The extension of the ocular ridge to the postero-lateral angles which, as above-mentioned, occurs in several species may likewise be the concentration of the nerve-supply which in Group 1 and 7. fimbriatus is split up into a convergent group of fine lines. The phylogenetic significance of these structures is discussed below.
A few remarks may here be made on the puzzling variations in the development of the meshwork on the genal areas which is found in this second group. The surface in some cases is covered with the reticulating ornament, but in other cases appears smooth or punctate ; and internal casts likewise differ much in their appearance. These peculiarities amongst individuals of the same species or members of the same group are due to the existence of more than one layer in the shell and to the difference in the characters of the outer and inner surfaces of these layers.
It seems that there are two layers to the shell, the outer one of which has an externally smooth or punctate surface, and is usually very thin and easily abraded, so that it is frequently missing from even well-preserved specimens. ‘The second or inner layer bears on its upper surface (which is in contact with the lower surface of the outer layer) the raised lines of the reticulating nervures, while the lower surface of the inner layer is only minutely granulated or smooth, the interlaminar nervures rarely showing through it. When, how- ever, this inner layer is thin and the nervures stout and strong, we find the reticulations showing through, and therefore impressed on the internal cast of the head-shiel ld, the ‘hexagonal or polygonal cells being represented as shallow pits, as can be seen in casts of Te Bucklandi from Girvan or of 7. seticornis from various English and Welsh localities. The nervures do not seem usually to project as raised lines on the inner surface of the inner layer; and the ocular ridge and tubercle are certainly hollow, for these structures show respectively as a groove and a pit on internal casts. When
Notices of Memoirs—Heterangiums vm Coal-measures. 128
the inner layer is thick and granulated, the internal cast is covered with corresponding small puncte. Barrande’ was much puzzled with these different appearances of the cheeks and ‘glabella, and did not offer any satisfactory explanation of them.
3. In the third group intv which I have arranged the species according to their genal characters, the adults have no ocular ridges and no ocular tubercles, and the reticulating nervures seem also to have disappeared, the shell being smooth and the interlaminar surfaces showing no meshwork, though puncte or minute granulations may be present. But in some of the largest specimens of 7. concentricus from the Oany River there are faint relics of the meshwork. The internal casts as well as the external surface of the shell only show minute pits or granules as a rule. In the young of TZ. concentricus the ocular ridge and ocellus of the species of Group 2 are present, according to Beecher, so that their loss seems to be a secondary modification or a suppression of larval characters; for the strati- graphically later group of 7. se¢icornis possesses them.
(To be concluded in our next Nwmber.)
NOTICHS OF MEMOTRS.
{.—Tse Hererancioms or tae British CoaL-mEasurES. By Dr. D. H. Scorr, For.Sec.R.S.
JILLIAMSON, in his published papers, only recognized two British species of Heterangium, Grievii and H. tiliwoides. Under the former name he included not only the Lower Carboniferous plant from Burntisland, on which the species was founded, but also certain Coal-measure forms from Dulesgate. In the joint work by Willamson and the present author the same nomenclature was adopted, but a second form from Dulesgate was also described under the provisional name H. cylindricum.
HT, tiliwoides, a Coal-measure species from Halifax, remarkable for the great development and perfect preservation of the phloem, has been kept distinct ever since its first discovery in 1886.
The enormous difference of age between the Burntisland and the Dulesgate plants rendered their specific identity highly improbable, and the latter has been separated under the name H. Lomazxii, originally suggested by Williamson himself, after the name of the discoverer, though not published. H. Lomaxii is characterized by the great distinctness of the primary xylem-strands, by their nearly exarch structure, with little primary centrifugal wood, by the abundant secretory sacs of the stele, and by the rather scattered leaves.
In the Dulesgate material several forms of Heterangium stem have been found in association; it is unlikely that they are specifically distinct—they more probably represent axes of different orders. The provisional species H. cylindricum differs in no important respect from LH, Lomaxit, to which it should be reduced.
1 Barrande, Syst. Silur. Bohéme, vol. i, Trilob., p. 622; ibid., Suppl., p. 47.
124 Notices of Memoirs—The Geology of Porewpine.
A very fine Heterangium from Shore was discovered by Mr. Lomax and his son in 1912. It is of large size, at least 17 mm. in diameter, though without secondary growth. The plant was originally compared with the so-called H. cylindricum, but is at least as close to H. tulieoides. The feature which at first seemed to be most striking is the fact that four distinct leaf-trace bundles enter the base of the leaf, each of them dividing into two in the petiole. This is certainly the best example yet found of a polydesmic petiole in Heterangium, and shows an interesting approach to the Medullosez in this respect. We may also compare Dr. Gordon’s new genus Rhetinangium. However, there is reason to believe that most of the British Coal- measure Heterangiums were polydesmic. In JZ. tilieoides there are four distinct bundles in the petiole, and the same was the case in H, Lomaxii.
In all these plants two bundles start from the stele to form the leaf-trace, dividing into four, at least in some cases, before entering the leaf-base. Only in a very small stem from Dulesgate (not associated with H. Lomaxit) did a single bundle leave the stele (as in the Burntisland species), dividing into two on its outward course. This. little stem has nothing to connect it with any other form and may be distinguished as H. minimum.
H1. tilieoides is maintained as a distinct species, mainly on the ground of its highly developed phloem with dilated medullary rays. In the behaviour of the leaf-traces it comes very near the Shore plant, which may, for the present at least, be kept distinct under the name HI. shorense.
II.—Nore on tHe Guronogy or Porcuprne.! By J. B. Tyreext.
HAVE been asked on two or three occasions whether I consider that the gold-bearing quartz veins in Porcupine are formed by
the filling of fissures or by replacement of the rock in which they occur, and I have told individual members of an instance where bodies of quartz were undoubtedly introduced into similar pre- Cambrian rocks by metasomatic replacement, but some others among those present might be interested in hearing of the instance, so I will mention it. In the West Shining Tree country greenstones showing strongly marked ovoidal or pillow structure, similar to that so common in the amygdaloidal basalts of this district, are particularly abundant, and here and there through the greenstone quartz veins. occur, some of which have been determined to contain gold. The. individual ovoids or pillows are packed closely together, but there are angular portions of the greenstone in between them, and, as a rule, the rock inside the pillows and in the angular areas outside of them are almost precisely similar in character. In one place, however, the angular areas are entirely converted into quartz, which, as far as I could see, was precisely similar to the quartz in the veins. near by. As these angular areas had originally been greenstone, we have in them a clearly marked example of a metasomatic replacement.
1 Extract from the Monthly Bulletin of the Canadian Mining Institute, June, 1915, pp. 397-8.
Reviews—J. B. Scrivenor—Geology of Malay States. 125
of the greenstone by quartz, but whether the veins in the vicinity were also formed by a similar replacement or not, I have no definite proof, but I believe that replacement took a large share in their formation. A number of the members here may think that such questions have no bearing on mining problems, and I have often heard men say that they did not care how the gold got into the rocks, that all they were interested in was where it was. Now the world has advanced too far to ignore the causes of things; if those things are to be clearly understood and if you are to clearly understand the bodies of ore which you are working you cannot afford to ignore the question of the causes which lead to the formation of those ore bodies, since a knowledge of those causes may enable you to correctly predict the extensions “of those ore bodies or may point y you to where other similar ore bodies occur.
RAV LH ws.
1.—Geotocy oF THE FeperareD Matay Srates. Geologists’ Annual Report for the year 1914. By J. B. ScrivEenor, Geologist F.M.S.
ARLIER reports, e.g. that for the period September, 1908, to January, 1907 (reviewed in the Groroeican Magazine, 1907, pp. 565-7), have given British geologists an opportunity of becoming acquainted with the general geology of the Federated Malay States, while Mr. Scrivenor’s finely illustrated report, Zhe Geology and Mining Industry of the Kinta District, Perak (1918), has described the district which is most interesting and important both geologically and economically. The present report, which deals principally with economic questions, is a record of steady progress, though it does not include any startling discoveries. There is only a brief reference to the field work of Mr. Scrivenor in mapping the Batang Padang district. Such work is bound to be carried out under many difficulties in view of the climate and of the dense vegetation which covers so Hee of this country.
Scrivenor took the opportunity a accompanying the district os of Upper Perak in a journey to the little-known region near the headwaters of the Perak River. He briefly describes the country as an area of granite at no great elevation, supporting masses of altered bedded rock with quartz porphyry and basic volcanic rocks.
The report shows that the chemist, Mr. C. Salter, has been occupied with economic work, chiefly assays for minerals, but including also a number of analyses. It is satisfactory to learn that Mr. Scrivenor is getting together a collection of photographs illustrating the geology of the country.
The author describes a successful attempt to replace the diamond by local corundum for drilling purposes. A consignment of kaolin was shipped to Kurope in order to ascertain if it could be used for pottery. Unfortunately, owing to the War, half the consignment failed to reach its destination.
Not much further information is given concerning the greatest industry of the peninsula, that of tin-mining, and no further light is
126 Reviews—H. Jeffreys—Interior of the Earth.
thrown on the question of the age and origin of the tin-bearing clays of the Kinta district, concerning which Mr. Scrivenor’s former assistant, Mr. W. R. Jones, is in disagreement with him.
There is a brief account of gold workings under native management. The statement that certain men ‘‘obtained in a season 2-3 katis of gold per party of three men. This is equal to 24-36 bungkals of gold”’ does not convey much information to the average reader of the report at home. Such words as prkul and ulu might also with advantage be explained in a footnote.
IJ.—Txe Inrerior or THE Harta.
Certain Hyporueses as To THE InTERNAL SrRucTURE oF THE Kant anD Moon. By Harrorp Jerrreys, B.A., M.Sc. Mem. Roy. Ast. Soc., lx, pt. v, pp. 187-217, 1915.
Tue Viscosrry or THE Earta. By H. Jerrreys. Monthly Notices Roy. Ast. Soc., xxv, pp. 648-58; Ixxvi, pp. 84-6, 1915.
Tue MecwanrcaL Propertizs or THE Karta. By H. Jerrreys. The Observatory, No. 491, pp. 347-51, 1915.
laa gradual refinement of geophysical methods of research
during recent years has resulted in the accumulation of quite a considerable fund of information relating to the interior of the earth. The known data from which our present knowledge is derived are—(1) the value of the precessional constant, (2) the earth’s superficial ellipticity, (8) the period of the variation of latitude, (4) the observed heights of oceanic tides, (5) the lunar deflection of gravity, and (6) the velocities of earthquake waves. Using the results available from these sources, Mr. Jeffreys discusses those hypotheses that regard the earth as consisting primarily of a metallic core surrounded by a rocky sheli, particularly from the point of view of determining the distribution of rigidity and density. He shows that neither the outer shell nor the inner core can be permanently rigid, and that the only conclusion consistent with the facts is that the earth as a whole is plastic. Again, the only distribution of density conformable with this conclusion is that of Wiechert, viz. a shell of density 3:2 surrounding a core of density 8-2 having a radius equal to 0°78 that of the surface. These figures are, of course, closely in accordance with the densities of stony and iron meteorites, and with the facts deduced from the seismic exploration of the earth’s interior. That the rigidity of the core is at least twice that of steel is a necessary consequence of the effect of pressure, if the main constituent of the core is metallic iron.
Mr. Jeffreys shows that the lithosphere has the hydrostatic form to a high degree of accuracy. This fact, combined with the deduction that the earth’s rotation was originally faster than now, leads us to conclude that the outer shell (at least) must have periodically adjusted itself to the hydrostatic form. Chamberlin has rejected this view, partly because it seems to imply that mountain ranges—particularly the older ones—should be meridional in their alignment. However,
it seems to the present writer that the greatest adjustment may —
have occurred in a period antecedent to any now recognized. Such
Reviews—Fossil Manumals from China. 127
adjustment, if accomplished mainly by movements of igneous magmas, would well explain the north to south elongation of the continents. Moreover, in this way one can understand the predominance of granitic rocks in the lighter continental segments, as compared with the suggested paucity or even absence of granitic rocks from the heavier oceanic segments,
In his consideration of the moon, Mr. Jeffreys finds that the period of revolution at the time of its consolidation was of the order 6°5 days. An important conclusion to which he arrives is that the strains within the moon can never have been sufficient to produce permanent set. It thus becomes difficult to believe that tidal friction has been responsible for the moon’s present attitude towards the earth. In the second paper it is shown that the moon’s empirical secular acceleration leads to such a value for the plasticity of the earth that the Eulerian nutation (responsible for variation of latitude) ought to. die down ina few days. One explanation of the obvious discrepancy would be that tidal friction is not the main factor now concerned in the control of the moon’s secular acceleration.
It is interesting to notice that none of these investigations prove a formerly molten earth, though it is safe to say that with such an assumption the present status and behaviour of the earth and moon ean be most easily explained. :
Artuur Hormes.
TIT.—(1) Ow some Fosstr Mammats From Szn-cuuan, Cutna. (2) On some Fosstu Mammats From Honan, Curna. (3) Ow some Fossin Mammats From 'l'suxinoxt, Uco. By H. Marsvomoro. Reports of the Tohoku Imperial University [2], Geology, vol. ii, No. 1, 1915.
‘{\HE first of these papers deals with mammalian remains from the
late Pliocene and early Pleistocene deposits. From the former _two species of Stegodon are recognized, together with a Rhinoceros and several Bovine animals, one of which is referred to a new genus Proboselaphus. From the latter horizon a new form of Hyena, H. ultima, and two species of Rhinoceros are described.
The second paper describes a number of Pleistocene mammals, including a large species of Hqwus, regarded as new, two species of deer, and a small Bison, referred to a new species under the name Bison exiguus. There is also a human sacrum which is said to resemble in several respects the sacrum of the Chapelle-aux-Saintes man described by Boule.
The last paper gives an account of a series of mammals from the Pleistocene of Japan, including Elephas namadicus and a new species of pig, Sus nipponicus, in some respects intermediate between Sus tatwanus and S. leucomystax.
- The above papers, which are published in English, are beautifully illustrated by a series of nineteen plates, for the most part unusually good photographs, and some text-figures.
128 Reviews—Mammoths and Mastodons.
IV.—Mammorus anp Masropons. By W. D. Marruew. No. 43 Guide Leaflet, American Museum of Natural History, November, 1915.
[* this guide leaflet Dr. Matthew has given a very interesting outline of our present knowledge of the Proboscidea, referring especially to the specimens exhibited in the American Museum of Natural History. He commences with a short historical account of the early discoveries of elephant remains, and then passes on to a brief description of the various extinct elephants, the American Mastodon, and the Tertiary Mastodons, concluding with a discussion on the early ancestors of the group and the general course of its evolution. One of the most interesting sections is that relating to the American Tertiary Mastodons, concerning which much more information than has yet been published is desirable. The author revives several forgotten generic names, e.g. Gomphotherium and Rhynchotherium, im the last case mentioning no species. Probably, however, the species described in this Magazine ([5] Vol. VI, p. 347, 1909) under the name Tetrabelodon dinothertoides should be placed here, the symphysial part of the mandible being deflected in the manner said to be characteristic of the genus. Jeritherium is not regarded as a direct ancestor of the Proboscidea, but, although it may be a side branch, its Proboscidean affinities appear to be incontestable. The pamphlet is illustrated with a plate and eleven text-figures.
V.—New Evryrrerrp Horton.—A Eurypterid in the Barton Beds! Sounds startling. And a coral-reef too!—Gently, gentle reader, these Barton Beds are in North America. Oh! But then, you will say (after some research) they are Stevenson’s Barton group in the Carboniferous of Pennsylvania. No, they are in Ontario, south of that superbly patriotic city Hamilton, and they lie at the very top of the Niagara formation. Fortunately Mr. M. Y. Williams (Oct., 1915, Canada Geol. Surv. Mus. Bulletin, No. 20) now proposes for them the name Eramosa beds, because their dark bituminous dolomites and shales are well exposed along the Eramosa River between Rockwood and Guelph. The importance of these beds lies in their paleontological evidence of a conformable passage from the Niagara to the Guelph formations. The Eurypterid, Husarcus logant, n.sp., is based upon various fragments, and since these are associated with fossils of marine origin, Mr. ‘Williams believes that the, arthropods ‘‘lived in an entirely - marine habitat ’’, a conclusion that would have been less open to criticism had the fragments been less fragmentary.
In the descriptions of species contained in these excellent Bulletins, would it not be possible to give some indication of their systematic position? How many geologists, or even professed paleontologists, ean say off-hand what ZLichenalia concentrica is? Mr. Williams tells them that the surface is undulatory and bears radial and concentric strie about 0°5 mm. apart; but he leaves them to their own devices to find out that it is a Wace pare 3S Bryozoan, closely allied to Listulipora.
it i me el it tarts ee a ee,
Reviews—Effects of Drought in the Waterberg. 129
ViI.—Errects oF Drovucut IN THE WaTERBERG, TraNsvAaL.—The Smithsonian Report for 1914 has reprinted from the Agricultural Journal of South Africa a paper by E. N. Marais on the effects of drought in the Waterberg, which has converted over 4,000 square miles of the Northern Transvaal, an area equal in extent to the ‘Orange Free State, once rich in orange groves, and formerly ‘a sort of lotus land of fertility, literally overflowing with milk and honey ”’ into an absolute desert ‘‘in which there is no single drop of water running or stagnant above the surface of the ground’’. He says the Limpopo River is now dry throughout this district, and water can only be obtained from it by deep sinking in its bed. All the ordinary ‘springs are empty, and it is only the thermal springs which are still flowing; they show no change in volume, though the loss of their water between the spring and the dam is 60 per cent greater than formerly. The animals have changed their habits or been extermi- mated; the vegetation is dead, and most of it has disappeared. The author refers to the hope that this extreme drought may mark the greatest swing of the pendulum towards desiccation and may be followed by improvement; but he remarks that every fact observed indicates that the change is permanent, and ‘‘ that the oscillations of the pendulum are gradually lessening round the dead point”. He regards this desiccation of the Northern Transvaal as part of a climatic change, which in the last fifty years has turned thousands of square miles of once fertile territory in Asia into desert. Mr. Marais’ descriptions are more graphic than convincing. His statement as to the habits of baboons’ are either exaggerated or refer to a local peculiarity ; and it is difficult to take many of the author’s statements seriously, as when he warns us that on the drying up of Lake Rudolf, “that most perfect diadem in the girdle of the globe . largely depends the fate of the Nile and of fertile Egypt.” Lake Rudolf contributes no more water to the Nile than it does to the Mississippi, and as the author’s African geography is so imperfect his conclusions on Asiatic climate do not carry weight.
VII.—Crimate oF Grotogic Trme.—Professor Schuchert’s ‘‘ Climate ot Geologic Time”’ has been reprinted from Huntington’s Climatic Factor (1914, pp. 265-89) in revised form in the Smithsonian report for 1914, pp. 277-311. The paper is a valuable summary of the chief factors as to the past variations in climate. There are no references, but as the authors’ names are quoted the authorities can be easily traced. The literature on the subject is so scattered that some is omitted, and the knowledge displayed from different parts of the world is unequal, but probably no geologist, even though specially interested in this question, can read the paper without finding much fresh. information. The author insists that the South Australian Boulder-clays are pre-Cambrian instead of Cambrian, and accordingly holds that there is no evidence of refrigeration of climate i in Cambrian times. He accepts the view that ‘‘ the typical glaciation ”, including perfect roches moutonnées and thousands of perched blocks in Western Ross and Sutherland are due to a pre-Cambrian and not to the DECADE VI.—VOL. Il.—NO. III. 9
130 Reviews—The Glacial Anticyclone.
Pleistocene glaciation. He adopts from paleontological evidence great climatic variations in the Mesozoic, but regards Neumayr’s Jurassic climatic belts as rather faunal realms. A universal warm | climate in the Middle Jurassic he claims from the far northern distribution of coral reefs and marine saurians, though why the saurians could not have lived in cold water, and the locality of the far northern Middle Jurassic coral reefs, is not stated. The identity of the tree ferns in Western Antarctica and Yorkshire does not appear to necessitate a universal warm climate, especially considering Hooker’s emphatic warning against trusting to ferns as climatic guides. The paper is of chief value as a summary of the opinion of one of the most competent authorities on paleontological evidence as to former geographical conditions. He concludes that there have been at least seven cool and four Glacial periods in the earth’s history, and that these were short in comparison with the intervening warm periods. In discussing the causes of the climatic changes he rejects volcanic dust as a primary factor, and also variations in the amount of carbon dioxide in the atmosphere. He regards the most probable cause as geographic changes due to rhythmic alteration in the earth’s topography, and he regards favourably the conclusion that there has been a periodic alternate heaping up of the ocean waters in the equatorial and Polar regions. He asks in conclusion, ‘‘ are we not forced to conclude’ that the earth’s shape changes periodically in response to gravitative forces that alter the body forms?”
VIII.—Tue Guactat Anricyctonr.—The growing belief that the former glaciations are to be explained by changes in the atmospheric circulation and especially by the influence of great stationary anti- cyclones is supported in an interesting paper by Professor W. H. Hobbs, ‘‘ The Role of the Glacial Anticyclone in the Air Circulation ot the Globe” (Proc. Amer. Phil. Soc., vol. liv, No. 218, pp. 185-225, 1915). Professor Hobbs is already well known as one of the upholders of this view, and he here discusses the bearing of the recent results from Antarctica and those collected by expeditions across Greenland which have not received adequate attention. Antarctica appeared at first opposed to this explanation owing to the belief that a great permanent cyclone lay around the South Pole. So strongly was this view accepted that Meinardus of the German Antarctic Expedition predicted that the interior of the Antarctic continent was bare and snowless. Meteorologists cling tenaciously to the South Polar cyclone. The results of the National Antarctic Expedition on this question were ambiguous owing to doubt as to whether the critical wind directions recorded were from the true or the magnetic south, directions which there are almost directly opposite. The work of the later expeditions has replaced the supposed South Polar cyclone by an anticline and has shown the existence of a powerful fohn effect around Antarctica, as is there also around Greenland. Professor Hobbs discusses the observations of the Swiss expedition under de Quervain, who in 1912 crossed Greenland from west to east between latitude 66° and 68° N.; and of the German expedition under Koch and
Reviews—Shketch of the Life of Eduard Suess. 131
Wegener, which in 1912-138 crossed between latitudes 72° and 78°. Professor Hobbs’ valuable memoir indicates that glacial geology will _ be advanced most from recent Polar work by the meteorological evidence.
TX.—Sxerca or tHE Lire or Epuarp Svuzss (1831-1914). By P. Trrurer. Smithsonian Report, 1914, Publication 2358, pp- 709-18.
(¥\HE Smithsonian Report for 1914(pp. 709-18) includes a translation
of the admirable sketch of Suess by Professor Termier, the Continental geologist who most approaches Suess in what has been called his geopoetic style. Professor Termier’s sympathetic and luminous eulogy lays stress on Suess’ Jewish origin, on the difficulties he encountered as a student in Vienna, which nearly drove him into commercial life, on his useful service in the municipal and national polities of Austria, on his two works, Die Hnstehung der Alpen and Das Anthtz der Erde, and on the intuitive nature of his mental methods. Professor Termier insists that the volumes of the Antilitz ‘‘contain scarcely any theories”. The author, he says, ‘‘does not seek to explain or convince—he shows.” He defends Suess from the criticism that on many controversial questions he adopted an indecisive and timid attitude, on the ground that Suess was never a theorist, that he did not care to argue on scientific matters, for he was content with seeing, and, having seen, with showing. He claims that Suess ‘‘ did not say all, he made few personal observations, he did not foresee everything, but by his intuitions, truly those of a genius, of relations and their causes, he incited, prepared, made possible decisive observations, observations which have revolutionized our ideas and illuminated our knowledge”’.
JE Wee Ge
X.—BrisiiograPuy oF YorksHire Grotogy. Forming Proceedings of the Yorkshire Geological Society, vol. xiii. C. Fox-Strangways’ Memorial Volume. By ‘Il. Suevparp. 8vo; pp. xxvi, 6380. London, Hull, and York, 1915. Price 15s. net.
T the time of his death Mr. Fox-Strangways had accumulated an y incomplete MS. towards a Bibliography of Yorkshire Geology from 1534 to 1892. This has been revised and brought up to 1914 by Mr. Sheppard of Hull, who has for many years contributed annual lists to the Waturalist. That it should be printed and issued by the Yorkshire Geological Society is an evidence at once of its value and the wisdom of that Society. Yorkshire geologists have now an encyclopedic work to hand to further their efforts and to save their time. Works are arranged chronologically, then follows a list of the maps and sections of the Geological Survey, and finally an index of 1380 double-column pages which gives subjects and localities much in the same way as the Annual Lists of Literature received by the Geological Society of London. It will be of extreme value to all local workers and scarcely of less to those at a distance,
132 Reports & Proceedings—Geological Society of London.
and is a really noble monument to Mr. Fox-Strangways, who did so much for Yorkshire geology. Mr. Sheppard has performed his share well, and thanks are especially due to him for undertaking so heavy an addition to his many burdens. We only wish so excellent an example will have imitators in many other of our county societies, for bibliography is a very sure and certain method of helping others and preventing duplication of work.
XI.—Sitvrran or tHE Lower SasxarcHewan.—From the Grand Rapids, from Cedar Lake, and from cuttings along the recently constructed Hudson Bay railway, various Silurian horizons are reported on by Dr. E. M. Kindle (Oct., 1915, Canada Geol. Surv. Mus. Bulletin, No. 21). Among Brachiopods two new species of Leptena (LZ. sinuosa and L. parvula) are described from beds of late Silurian age, equivalent to the Stonewall Limestone. A dolomite near the base of the Silurian at Grand Rapids abounds in Conchidium decus- satum. The numerous ventral valves of this Pentamerid show variation in three well-marked directions, but intermediate forms are so numerous that no distinct varieties can be recognized. In a word the variation appears continuous. The spondylium reaches approxi- mate maturity at an early stage, but the radiating folds continue to increase in strength and number down to extreme old age.
REPORTS AND PROCHHDIN GS.
I.—GeronogicaL Socrery or Lonpon.
1. December 15, 1915.—Dr. A. Smith Woodward, F.R.S., President, in the Chair.
Dr. Aubrey Strahan, F.R.S., gave an account of a deep boring which was made in 1918 in search of coal, in the parish of Little Missenden, at an elevation of 459 feet above sea-level. The collection of specimens and the identification of fossils was carried out by Mr. J. Pringle. For the first 1,200 feet the hole was punched, and nothing is known of the strata traversed down to that depth—beyond the fact that the boring started in the top of the Middle Chalk and passed through some Oxford Clay and, below that, some oolitic limestones which presumably belong to the Great Oolite Series. From 1,200 feet the hole was drilled for 64 feet, and cores were preserved. The cores consisted of alternations of limestone and mud- stone, with a rich and characteristic Upper Ludlow fauna. Among the fossils was Orthoceras damesi, Roemer [? Krause], which had not previously been obtained in this country.
The boring serves to fix part of the northern boundary of the tract of Old Red Sandstone which underlies London. It is intended to publish a full account in the next issue of the Summary of Progress of the Geological Survey.
Reports & Proceedings—Geological Socrety of London. 133
2. January 5, 1916.—Dr. A. Smith Woodward, F.R.S., President, in the Chair.
The Secretary read the following communication :—
‘The Islay Anticline (Inner Hebrides).”” By Edward Battersby Bailey, B.A., F.G.S., 2nd Lieut. R.G.A.
The observations made by Peach, Wilkinson, Thomson, Macculloch, and others in regard to the ‘ Schistose Islands’ of Scotland are passed in review, and many of them confirmed. In certain directions, however, new interpretations are offered. The following suggestions are among those put forward :—
1. An important fault, perhaps the Great Glen Fault, passes through the hollow separating Colonsay and the western peninsula of Islay from the rest of the archipelago.
2. The dolomitic ‘Fucoid Beds’ of Wilkinson and Peach are not the highest geological subdivision of the district, either strati- eraphically or structurally. hey are earlier than, and structurally they underlie, the greater part of the Islay Quartzite, as well as the whole of the Port Ellen Phyllites and Easdale Slates.
3. In conformity with the previous paragraphs, several correlations must now be abandoned. Thus the Scarba Conglomerate is not the equivalent of the Portaskaig Conglomerate, but is of considerably later date.
4, Small-scale isoclinal folding is of less significance in the greater part of the district than has sometimes been thought. The main feature of the tectonics of Eastern Islay is a comparatively simple isoclinal anticline overthrown towards the north-west upon the Loch Skerrols Thrust. The thrust itself has been well described by Dr. Peach and Mr. Wilkinson.
5. Finally, grounds are given for believing that an accurate knowledge of the structure and rock-concession of Islay is of crucial importance in determining the tectonic plan of the West Highlands generally. :
3. January 19, 1916.—Dr. A. Smith Woodward, F.R.S., President, in the Chair.
The following communication was read :— “The Physical Geography of Bournemouth.” By Henry Bury, MAAC ES S., H.G-.S.
_ The curves of the plateaux in the Hampshire basin (including that of Bournemouth) show a marked relation to the main river-valleys, indicating that the latter were already in existence (though probably much less deep than now) before the plateau-gravel was deposited. On the other hand, the fact that this gravel everywhere covers the main watersheds is inconsistent with the theory of deposition on simple river-terraces, and points to widespread floods and the formation of gravel-sheets at one or more periods. Paleoliths are most frequent at low levels (below 140 feet O.D.), but occur up to 350 feet O.D., where their presence must be due either (1) to a vast accumulation of gravel in Chellean times, or (2) to channelling at later dates. Both hypotheses present difficulties.
134 Reports & Proceedings—Geologicul Society of London.
The Chines along the coast of Bournemouth Bay did not originate at the cliff-edge and grow inland, as generally stated, but are the over-deepened bottoms of older and longer valleys. A similar double structure is seen in the Chines of the south-western corner of the Isle of Wight, where it is due to the destruction of part of the valley of the Yar by the sea since the deposition of the valley gravel; and it is suggested that the Bournemouth Chines are due to the breach of the Solent River by the sea at the same late period. The 140 ft. bluff, running all across Hampshire to the sea-cliff at Goodwood, is comparable with the 100 ft. terrace of the Thames, and was probably formed in an estuary in pre-Chellean times.
The rate of recession of the cliffin the western part of Bournemouth Bay is estimated at about 1 foot per annum. It may be more in the eastern part, but the estimate of 3 yards per annum near Christchurch, made in the Natural History of Bournemouth, is probably much too high; and the reasons given in that volume for local variations in rate cannot be accepted.
The angle of the cliffs is said to have become steeper of late years ; but this is not true of the western part of the bay, and it is desirable that the observations on which the belief rests should be published.
4. February 2, 1916.—Dr. A. Smith Woodward, F.R.S., President, in the Chair.
A lecture was delivered by Richard Dixon Oldham, F.R.S., on the Support of the Himalaya.
He said that it was known that the major prominences of the Earth’s surface are in some way compensated by a defect of density underlying them, with the result that they do not exert the attractive force, either in a vertical or in a horizontal direction, which should result from their mass. <A study of the distribution of this com- pensation shows that there is a general balance between it and the topography, such that the weight of any vertical column through the crust of the earth is, on the average, constant, whatever may be the elevation of the surface. ‘To this condition the term isostasy has been applied, which does not merely denote a static condition, but implies a power of adjustment of the compensation to the variation in load produced by surface denudation and transport.
The explanations that have been proposed of the existence of compensation fall into two classes. One supposes the relief of the surface to be due to an alteration in the volume of the underlying rock, and may be regarded as hypotheses of tumefaction. ‘They involve no addition of matter to the crust under a mountain range, and do not provide, either for any departure from-a balance between topography and compensation, or for a restoration of the balance when disturbed by denudation. The other group of hypotheses attributes the origin of the range to a compression of the crust, the injection of molten matter, or the ‘undertow’ of the lower part of the crust. To provide for compensation any hypothesis of this class will require a downward protuberance of the nether surface of the crust, causing a displacement of denser by lighter material, as also an
Reports & Proceedings—Geological Society of London. 135
effect of buoyancy owing to this difference of density: this group of hypotheses, therefore, may be regarded as one of support by flotation. They involve a migration of matter from outside to beneath the range, they allow of a considerable local departure from exact balance between load and support (or topography and compensation), so long as the defect in one tract is balanced by an excess in an adjoining one, and they provide for an adjustment of any disturbance of this balance.
The geodetic observations in the Himalayas show that there is a defect of compensation in the outer hills, which increases in amount until at about 50 miles from the edge of the hills it reaches an equivalent to an overload of about 2,000 feet of rock. In the interior of the Himalayas the only observation yet published shows that at about 140 miles from the edge of the hills this overload has disappeared, and compensation is in excess. The variation in the balance between topography and compensation points to one of the second group of hypotheses, to a support of the range by flotation, and to the conclusion that the growth of the support has been more rapid than that of the range. The primary problem then becomes, not as to how the Himalayas are supported at their actual height, but why they are not even loftier; in other words, the problem is carried one stage farther back, from the origin of the range to the origin of its ‘ root’.
This result of the examination of the geodetic data simplifies the explanation of some difficult geological questions. It affords an easy explanation of the indications which are found in the interior of the Himalayas, and of other similar ranges, of simple vertical uplift without disturbance, and also of the manner in which the contorted and faulted strata, the disturbance of which must have taken place under the pressure of some thousands of feet of rock, have been brought up to a level where they are exposed to denudation and their structure revealed; but it brings us very little nearer to an explanation of the ultimate origin of the range. It is a distinct step forward in illustration of the mechanism of the production of mountain ranges of the type of the Himalayas and the Alps, but we are as far as ever from an understanding of the power by which this mechanism is driven.
ANNIVERSARY MEETING.
5. February 18, 1916.—Dr. A. Smith Woodward, F.R.S., President, in the Chair.
The following Awards of Medals and Funds have been made :—
The Wollaston Medal is awarded to Dr. Alexander Petrovich Karpinsky, in recognition of his researches concerning the Mineral Structure of the Earth, especially in connexion with the Geology and Paleontology of Russia.
The Murchison Medal, together with a sum of ten guineas from the Murchison Geological Fund, is awarded to Dr. Robert Kidston, in recognition of his valuable contributions to Geological Science,
1386 Reports & Proceedings—Edinburgh Geological Socrety.
especially in connexion with the Flora and Stratigraphy of the Carboniferous Rocks.
The Lyell Medal, together with a sum of twenty-five pounds, is awarded to Dr. Charles William Andrews, as an acknowledgment of the value of his researches in Vertebrate Paleontology.
The Balance of the Proceeds of the Wollaston Donation Fund is awarded to Mr. William Bourke Wright, in recognition of his contributions to Quaternary Geology.
The Balance of the Proceeds of the Murchison Geological Fund is awarded to Mr. George Walter Tyrrell, in acknowledgment of his contributions to petrography, especially in connexion with Igneous Rocks in Scotland.
A moiety of the Balance of the Proceeds of the Lyell Geological Fund is awarded to Mr. Martin A. C. Hinton, in recognition of his. researches on the British Pleistocene Mammalia.
A second moiety of the Balance of the Proceeds of the Lyell Geological Fund is awarded to Mr. Alfred Santer Kennard, in recognition of his work on the Pleistocene Deposits of the South of England, and on their Molluscan Fauna.
The thirteenth Award from the Daniel Pidgeon Trust Fund was made on March 24, 1915, to Edward Talbot Paris, B.Se., who proposed to continue his researches on the Lamellibranchia of the Rheetic, Lias, and Lower Oolites of England.
II.—Epinsures Geroroeicat Socrery. 1. December 15, 1915.—Dr. Robert Campbell, President, in the Chair.
1. ‘‘ Professor George Sinclair’s ‘Short History of Coal’, published in Edinburgh 1672.”” By D. Tait.
In this paper Mr. Tait brought before the notice of the Society a work called The Hydrostaticks, written by George Sinclair, Professor of Philosophy and Mathematics in the University of Glasgow, who is best known as the author of Satan’s Invisible World Discovered, a book on ghosts and witches. A section of Zhe Hydrostaticks is entitled ‘‘ A Short History of Coal’’. In it is given the first account of the Midlothian coalfield. The outcrop of the ‘ great’ seam of coal is traced round the basin and also in the neighbourhood of Prestonpans and Tranet in a remarkably accurate manner. He notes that whin dykes often render coal-seams with which they come into contact as if they had been burnt, and records many other interesting geological facts in the neighbourhood.
2. ‘‘A Diatomaceous Deposit at the East End of Loch Leven, Fifeshire.”” By J. Duncan. With Note on the Diatomaces by George West. i
This deposit forms part of the alluvial flat at the east end of Loch Leven. It was first observed in a trench cut for a water-pipe track near the Old Gullet Bridge, which crosses the former course of the River Leven near Lochend farm-house, and afterwards traced eastwards to East Bowhouse, a distance of about two miles. The greatest thickness of Diatomite met with in the series of pits made
Reports & Proceedings—Hdinburgh Geological Society. 137
was 1 foot. It is not continuous over the area, but occurs in patches on slightly raised ground. Some parts of this deposit may be of commercial value for use as an abrasive.
A microscopic examination of the deposit was made by Mr. G. West, of the Botanical Department, University College, Dundee, who makes. out a list of thirteen genera of diatoms.
2. January 19, 1916.—Dr. Robert Campbell, President, in the Chair.
1. ‘Notes on the Former Courses of the River Devon.” A suggested Evolution for part of the River System of Fife and Kinross. “(With lantern illustrations.) By J. E. Wynfield Rhodes, B.Sc., M.I.M.E.
In this paper an attempt is made to trace out the evolution of the valleys of the Rivers Devon, Eden, Leven, and their tributaries. Starting from the assumption that the original or consequent drainage was E.S.E., an assumption justified by the study of other districts on our eastern seaboard and in entire harmony with the evidence obtainable locally, the positions of two of the original streams A and Bare postulated. This constitutes the first stage in the evolution, and the gradual development of our present river system in this area is shown to occur in four subsequent stages. The course of stream A is marked by the following valleys: Glen Lednock, Glen Eagles, Glen Devon, the Gairney Water Valley, Blairadam windgap, and the Chapel Burn. Stream B was parallel to it, and its site is marked by the S. Queich, Loch Leven, and the Lochy Burn. Stream A is beheaded at Muthil, thus producing the obsequent Glen Eagles Valley, and near Cardenden by the River Ore, a tributary of stream B. Subsequently a stream cutting back along the Ochil fault beheads stream A at the Crook of Devon and the River Devon is produced. In the next stage the strike stream Eden beheads both A and B and develops the Plain of Kinross ; Blairadam and Ballingry windgaps are thus produced. Finally, in the Glacial period, Loch Leven is produced by a drift dam at. Mawearse, the waters of the lake escaping by the Leven Valley.
2. ‘‘Veining and Metasomatism in Basalt at Upper Whitfield, near Macbiehill. ”. (With lantern illustrations.) By T. Cuthbert Day, F.C.S.
The author recognizes the great variety of ways in which veining may occur in igneous or in sedimentary rocks, and does not pretend to put forward a theory of uniform application. He merely describes a particular case, and seeks to maintain that the veining in the basalt at Upper Whitfield has not been caused by infiltration of mineral matter into ready formed fissures or dislocations in the basalt, but by a methodical replacement of the basalt along the layers of exfoliation, the basalt itself being removed piecemeal and its place taken by veining material. An example of what might be considered as metasomatism in the same basalt is also described, the prime cause of the alteration being due to some defect in the part of the basalt at the time of intrusion which rendered it liable to attack by mineral solutions. An attempt is made to explain the order of the changes
|
188 Reports & Proceedings—Geological Society of Glasgow.
in the basalt, the first being a large replacement of the basalt by a deposit of siliceous material, which was itself subsequently, in a considerable measure, removed and replaced by a deposit of calcite.
‘II1I.—Geronoeicat Soctrry or Grascow.
At a meeting of the Geological Society of Glasgow, held on January 18, 1916, Mr. Alex. Scott, M.A., B.Sc., read a paper on ““The Physiography of Glen Lednock’’. He pointed out the place of Glen Lednock in the general valley system of the Highlands, and said that the glen now contained a number of dry river channels, only one of which was now in use. It was pointed out that the fragments, now isolated, could be pieced together with fair certainty. The position of each of these fragments was described, and the reasons for their formation and successive abandonment discussed. Most ot these channels are fairly shallow and open, but at the Deil’s Cauldron the stream has cut a deep gorge, and this has been done by pothole action, as very fine examples of these are to be seen in the walls. In this case the dip of the beds seems to have played an important part in determining the position of the channel, but in other cases the junction between hard and soft rocks seems to have been the controlling factor.—Professor Gregory complimented the author on his paper, and agreed with him that Glen Lednock was of great antiquity and probably pre-Glacial. He also pointed out that it was only by the study of these river valleys that it was possible to elucidate the history of Scotland during the long period between Tertiary and post-Glacial times, as there were no deposits of that age in Scotland to contain a record. The study of this and similar glens also threw light on the question of whether movement was constantly proceeding on the line of the Highland Boundary Fault. The existence of a sudden drop in the beds of such glens points to there having been a sudden uplift of the country north of the fault in comparatively recent times.—In reply the author stated that the apparent rejuvenation of these glens does point to an uplift, but it may be due to another cause. In Glen Turret, however, the burn is cutting Old Red Sandstone on both sides of the fault, and therefore the pronounced fall in that glen supports Professor Gregory’s suggestion. He agreed with Mr. Macnair that dykes do have some connexion with the direction of the gorges.
‘‘On an Ancient Shore-line.”? By M. Macgregor, B.Sc., H.M. Geological Survey. The Helmsdale Boulder Bed, with which the paper deals, dated from late Jurassic time, and consisted of a tumultuous accumulation of blocks, the majority angular, embedded in shales, sandstones, and shelly limestones which were contorted at the points of contact. The boulders had been determined as all of Middle Old Red Sandstone age, with a regular ascent in the series from north to south. The age of the bed had been determined by means of its plants as Kimmeridgian, and by means of a coral as Portlandian. ‘The author described the structure of the district and summarized the views on the origin of the boulder bed of various authorities who had examined it. These opinions were shown to be untenable from
Reports & Proceedings—Liverpool Geological Society. 139
one circumstance or another, with the exception of that briefly stated by Woodward in 1910; he suggested that the boulder bed was an accumulation of debris dropped from sea-cliffs into deep water. No theory of water transport could account for the presence of a boulder 190 x 50 X 80 feet, consisting of frequent alternations of fissile sandstone, etc., and there is no J evidence of glacialaction. The author suggested that the boulder mentioned was just a sea-stack which had capsized, and showed a series of photographs of the boulder bed and of the scenery of the present Old Red Sandstone cliffs of the Sutherland | coast, pointing out how the conditions of these would give rise to a deposit possessing exactly the characters of the boulder bed.— Professor Gregory congratulated Mr. Macgregor on having solved a problem that had baffled so many authorities. The solution showed that Old Red Sandstone strata must have covered that district as recently as late Jurassic times.
1V.—Liverroot Gronoeicat Soctery.
February 8, 1916.—-J. H. Milton, Esq., F.G.S., F.L.S., President, in the Chair.
The following paper was read :—
‘‘The Origin of the Trias: a restatement of the problem.” By H. W. Greenwood.
The author reviewed and criticized previous theories in the ight of recent work, and considered them to be based largely on a mis- interpretation of facts, conditions having been assumed which have not yet been proved to have existed. The principal conclusions at which he had arrived were: (1) That no true line of demarcation existed in Great Britain between the Permian and Triassic systems, which must be dealt with as a whole. (2) That present-day topography was a partial restoration of pre-Triassic topography. (3) That the material of the various British Trias deposits had been derived from different sources, and that no general theory of river or desert origin was applicable to all or any of the deposits. (4) That the evidence pointed to arid climatic conditions existing between the close of the Carboniferous and beginning of the Jurassic periods. (5) That the Trias deposits of the Liverpool district, Cheshire, and the Vale of Clwyd were all derived from the same source, which lay to the west and south-west, and that the Bunter and Keuper divisions were unconformable. The high content of calcium carbonate which chemical analyses had revealed was:an original character, and due to the denudation of Carboniferous Limestone and Coa]- measures.
V.—MInERALOGICAL Socrery.
January 18, 1916.—W. Barlow, Esq., F.R.S., President, in the Chair.
Professor G. Cesaro: A simple Demonstration of the Law of Miller. In any spherical triangle the arc x joining the apex C to a pole dividing the base ¢ into segments a and # is given by the equation cos cos ¢ = cosa sin B+ cos b sin a. Taking the apex as the pole
140 Reports and Proceedings—Mineralogical Society.
of one of the axes and the base as the zone containing the four poles, the usual anharmonic ratio is obtained. — Dr. G. T. Prior: The Meteorite of Daniels Kuil. The meteorite consists of nickeliferous. iron in large amounts, troilite, oldhamite, felspar, and enstatite, free from iron, and thus belongs to the exceptional Hvittis and Pillistfer group of chrondritic stones, to which also must be added the Khairpur meteorite, which contains notable amounts of oldhamite.—Dr. G. T. Prior: On the Relationship of Meteorites. Meteorites may be arranged by their chemical and mineral composition into the following six groups—(1) Bustee and Hvittis group, (2) Siderolites, (3) Cronstad group, consisting of chondrites containing over 10 per cent of nickeli- ferous iron, (4) Baroti group, consisting of chondrites containing less than 10 per cent of nickeliferous iron, (5) Chladnite group, including Chladnites, Angrites, Chassignites, Amphoterites, some Rodites, and probably some Chondrites containing little nickeliferous iron, (6) Eucrites, Nakhlites, Shergottites, Howardites, and some Rodites. It is suggested that from the first group the remaining stones have been derived by the interaction between oxidizing nickeliferous iron and enstatite, with consequent production of ferriferous olivine and bronzite, the formation of chondrules, and enrichment in nickel of the residual iron. The nickeliferous iron of the first three groups corre- sponds to the more common meteoric irons, such as the octahedrites and hexahedrites, containing less than 10 per cent of nickel, and that of the last three to nickel-rich Ataxites, containing more than 10 per cent. of nickel. The groups (2)-(6) contain progressively diminishing amounts of nickeliferous iron, which is increasingly rich in nickel, and have increasing amounts of ferrous oxide in the ferro-magnesium silicates, in which the ratio of magnesium to iron atoms approximates. in the case of group (2) to 7, of group (8) to 5, of group (4) to 34, of group (5) to 2, and of the last group to 1 or less.—Dr. J. W. Evans: The isolation of the directions-image of a section of a mineral in a rock-slice. In some optical investigations, e.g. the observation of the interference-figures of minerals in thin sections under the microscope, the determination of the angle of total reflection, and the measurement of crystal angles, the image studied is not that of the object, but is one in which every part corresponds to a direction in which light is transmitted, or in other words it is a directions- image. To prevent the effects of closely adjoining objects being blended all light except that traversing the object under investigation must be screened by a diaphragm placed near it or in a position conjugate with it. In an ordinary petrological microscope this may often be conveniently effected by placing the diaphragm below the condenser, so that the image of the aperture is seen in focus simultaneously with that of the object. The. best results are, however, obtained when the diaphragm is placed in the focus of the eve-piece, and, after it has been adjusted, the Becke lens placed above it. The same method may be employed with advantage in the other observations referred to, the instrument employed being constructed primarily as a microscope, and converted into a telescope by the addition of a lens, instead of vice versa as is the usual procedure.— Dr. J. W. Evans: A new method of determining the angular direction
_ Correspondence—T. G. Bonney. 141
represented by a point in the directions-image. A circular plate is ruled with concentric circles at distances from the centre equal to r tan 0, where @ stands for different angles at intervals of 5° up to the full aperture of the objective and r as a constant length, say 50mm., and with radiating lines 5° apart; it may be placed on supports which fix its position above thestage. When the microscope is adjusted for observations of the directions-image of a mineral, the point, the angular position of which is to be determined, is identified by the end of an adjustable pointer, which is placed so as to be seen in focus. The microscope is then focussed up until the objective is accurately at a distance + from the plate, which is now placed in position and is clearly seen. The angular position required is then shown by the position of the end of the pointer relatively to the scale of the plate.—L. J. Spencer: A new (seventh) List of Mineral Names.
CORRESPONDENCE.
Pit Uae ON GLACIER LAKE CHANNELS.
Srr,—As I have stated my case at some length in regard to the “overflow channel’ valleys, and as Professor Kendall and Mr. B. Smith in their courteous criticisms restrict themselves mainly to points of detail, most of which had been noted in my pamphlet, while omitting to discuss the fundamental difficulties to which I called special attention, I must not weary your readers with more than a few words. ach of them, I may remark, has confined himself, perhaps wisely, to the district which he has made hisown. Hence they have not dealt with the Ringstead Down ‘railway trench’ (which is perfect from its head to its end, besides having a lateral tributary of more normal form), or with the ancient and more modified trenches near Hawes Junction andin the Dufton Pike district, or with those in the Cleveland and Black Combe districts, which are occasionally perfect or are suggestive of decapitation. Nor have they met my objection that the shape of the trenches is not such as should be the result of an overflow from an ice-dammed lake (see my pamphlet, pp. 7 and 8), for what Professor Kendall does say on this subject seems to me hardly to meet my objection. He and Mr. B. Smith lay much stress on the fact that spurs are severed by channels transverse to the valleys by which those spurs are defined, no doubt a thing not easily explained, but they apparently forget that similar and similarly situated trench valleys occur in the Dufton Pike district and in that to the south of Cader Idris, where the lake overflow hypothesis seems to me an impossible explanation. Nor, so far as I can see, does the ‘‘ marginal drainage of an ice-sheet’’ really help » us. Of course that would erode, but so far as my experience goes (and it is a fairly large one) it would find the cutting of a flat- bottomed trench very difficult and that of an ‘in-and-out’ impossible. Much of what Von Engeln says of marginal drainage is familiar to me, and the channels cut by it are not ‘railway trenches’ but nearer to gorges. Also, Mr. B. Smith forgets to mention that the granite
142 Correspondence—Christian Tinne.
in which channels were quickly cut was ‘‘ very much shattered by close jointing”. It is no doubt a little remarkable that, supposing these trench valleys to be, geologically speaking, rather ancient, their sides are not more furrowed; but water-worn valleys in the Bunter pebble-beds, the Neocomian Sands, and the Chalk downs of Southern England often have their sides unfurrowed, and cliffs of limestone, on a comparatively small scale in England and on a gigantic one in the Alps, are frequently smooth for considerable distances, showing that atmospheric denudation has about kept pace with that from streamlets. The same sometimes holds good with sandstone and granite. Finally, they forget that the invasion of the larger part of England
by great ice-sheets is just as much an hypothesis as that of sub- mergence, and cannot be regarded as an axiom until the difficulties to which I have repeatedly referred have been fairly met (instead of being ignored) and removed. I may add that I cannot accept as moraines (with which I ought to be familiar) several of those to which some geologists give that name. But my pamphlet will fulfil its purpose if it leads to a more careful study of the whole question, instead of such reasoning as this: ‘‘ Here is a peculiar valley: how can we associate it with terrestrial ice-sheets?’? To me the safer ‘method seems this: ‘‘ Here are certain physical facts: what inference do they suggest ?”’ Ido my best to keep ‘‘ my mind from being set awhirl”’ when it arrives at a conclusion which is contrary either to a popular opinion or to what I was taught in my younger days.
T. G. Bonney.
A METHOD OF HARDENING FRIABLE FOSSIL WOOD FOR SECTION-CUTTING.
Sir,— While collecting from the Lower Gault in the neighbourhood of Farnham, Surrey, I often found fragments of what was evidently driftwood lying amongst the shells. It was extremely friable; in fact, when dry, it was, as a rule, impossible to touch it or even blow upon it without causing it to fall away in powder; and to obtain a section from such material seemed well-nigh impossible.
When treated in the usual way with silica solution the wood did not appear to be permeated, but merely to be—in the mechanic’s term —‘case-hardened,’ that is, to have formed on the surface a very thin erust of hardened substance, rendering the specimen useless for section-cutting.
It occurred to me, however, that a better result might be obtained by forcing the silica solution into the wood, on the same principle as that by which railway-sleepers are impregnated with creosote under pressure. An ordinary model steam-engine boiler was, accordingly, adapted for the purpose. First the filling hole was enlarged enough to admit a piece of the wood, and a certain fitting, stocked by all model makers, added. This consists of an ordinary bicycle tyre valve threaded on the outside to screw into the boiler. This attached, sufficient silica solution (undiluted) was poured in to cover the wood, the filler-cap screwed on, and the boiler pumped up with an ordinary eycle-pump. The pressure was raised to 30 lb. per square inch,
Obituary—Cownt Solms-Lawbach. 143
and the whole left for five days, except that it was occasionally pumped up to maintain the pressure, which dropped rather rapidly ; in fact, on several occasions, namely at night, there can have been no pressure at all for some hours, as it was always necessary to have recourse to the bicycle pump in the morning. On being taken out after five days, the wood was found to be much harder, or rather, it was tough—I could make no impression on the wood by scratching with my finger-nail, but it had a hard /eathery feeling when scratched. It was now allowed to dry by simple exposure to the air in my workshop, and in six days more appeared to be dry.
I should add that before hardening it as above described I had managed to cut one end of the wood flat, across the grain. The wood being dry, I now attempted to polish it by simple rubbing against a soft cloth, and obtained a fair polish, but, not having the necessary apparatus or skill to cut a section, I gave the specimen to the British Museum of Natural History, where it now is. Hoping that this description may be of use to others.
Curistian TINNE.
THE CHINE, WRECCLESHAM, FARNHAM. January 6, 1916.
WILLIAM SMITH’S MAPS.
Srr,—I am preparing a monograph on Smith’s maps, ete., for the Yorkshire Geological Society, and am anxious to see a ‘‘ Reduction of Smith’s large Geological Map of England and Wales intended as an ‘elementary map for those commencing the study of Geology, 1819”, referred to in Phillips’s Memoirs of Smith.
- I find that Smith’s large maps of 1815 often bear a signature and a number, such as ‘‘ No. 66” or ‘‘a 33”. If any readers of the GxrotocicaL Macazrinz possess copies of this large map, perhaps they would kindly inform me what number the map bears. It occurs under the ‘‘ Section of Strata”, which appears on the map to the east of the Humber estuary.
T. SHEPPARD.
THE MUSEUMS, HULL. January 25, 1916.
OBITUARY.
HERMANN GRAF ZU SOLMS-LAUBACH, Sc.D., For. M. Roy.Soc., For. M. Linn. Soc., For. M.Gerot. Soc. BorRN DECEMBER 23, 1842. DIED NOVEMBER 24, 1915.
Count Sotms-LavsacH was well known amongst men of science as a most distinguished botanist. His death was communicated to this country by Professor A. G. Nathorst, the Swedish Paleontologist of Stockholm.
Count Solms was born in 1842, and was in his 73rd year. He devoted his life wholly to science. He was Professor of Botany at Gottingen and afterwards at. Strasburg, from which he retired a few years since.
144, Obitwary— Thomas Sergeant Hall, D.Sc.
His work extended to every department of botany. Perhaps the most important of all was that on fossil botany. He was an intimate friend of the late Professor Williamson. His Paldéophytologie, published in 1887, was translated for the Oxford Press in 1892. In it the author impresses on botanists the value and significance of the geological record as affecting plants.
Of special importance may be mentioned his paper on Bennettites ‘Gibsonianus, a fossil Cycad from the Isle of Wight; on the
‘Cycadofilices, Protopitys, Medullosa, ete.; on Devonian and Lower
‘Carboniferous Plants; and on Psaronius.
He was elected a Foreign Member of the Linnean Society in 1887, of the Royal Society in 1902, and of the Geological Society in 1906. He received the Gold Medal of the Linnean Society in 1911, and was madea Sc.D. of the University of Cambridge at the Darwin,celebration in 1909.
[D. H. S. From Nature, January 13, 1916. ]
THOMAS SERGEANT HALL, M.A., D.Sc. BoRwN 1858. DIED DECEMBER 21, 1915.
A sERious gap has been made in the ranks of Australian geologists by the deeply regretted death of Dr. Hall, on December, 21, 1915, at the comparatively early age of 57.
Dr. Hall occupied the post of Lecturer in Biology at the Melbourne University, where he was greatly esteemed as a teacher. He was perhaps better known abroad as an ardent geological worker amongst the Victorian graptolitic and Tertiary rocks. In 1899 he contributed an important paper to this Magazine on ‘‘ The Graptolite Rocks of Victoria, Australia’’. In recognition of his work on the distribution of Australian graptolites, embodied in many important contributions to various journals, he was made the recipient of the Murchison Fund of the Geological Society of London in 1901. The subdivisions of the Victorian Ordovician rocks were suggested and worked out in detail by Dr. Hall. He had also devoted much time to the study of the interesting and somewhat complex series of Tertiary fossiliferous strata of Victoria, generally in conjunction with Dr. Pritchard ; and these authors originated the useful local terminology now usually
applied to the subdivision of these rocks. In all his undertakings —
Dr. Hall was very thorough, and his intimate knowledge of the
biological side of the science added to the value of his paleontological _ work. Always ready to help his confréres, especially in the domain of scientific literature, he will by them be greatly missed. His book on Victorian Hill and Dale has done much to foster a popular taste for outdoor geology, and his series of chatty articlesin the Australasvan on current scientific topics under the pen-name of Physicus were widely read. In the cause of maintaining a high standard for our Victorian scientific libraries, and especially that. of the Royal Society of Victoria, of which he was the Hon. Secretary for fifteen years and President in 1914-15, Dr. Hall did significant service, which alone would justify his high reputation as a devoted scientific worker.
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I. ORIGINAL ARTICLES.
Two large Obsidianites from the Raffles Museum, Singapore. By Je BS SCRIVENOR, M.A., F.G.S. = (Plate VII.) ..
Ball or Pillow-form. Structures in Sandstones. By BERNARD SMITH,
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Il. Revinws.
Professor J. Joly. Radio-activity .
G. D. MeGrigor. Field Analysis of Minerals ...
J. _V. Lewis. Determinative Mineralogy ...
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REVIEWS (continued). Rutley’s Elements of Mineralogy . 179 Lawson’s Profiles of the Desert ... 180
Brief Notices: ‘Triassic Rocks of Wirral— Zoogeography—Form of the Harth — Shallow - water Deposits—Faunistic Influence— Geologists’ Association — The Zoological Record — Obsidian from Iceland cel SOs
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Geological Society of London . 182 Hdinburgh Geological Society . 188 TV. CORRESPONDENCE.
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Professor J. Wesley Judd - 0)
VI. MISCELLANEOUS.
The Closing of National Geological Collections ... . 192
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TWO LARGE OBSIDIANITES (nat. size), FROM THE RaFrFrLtes MuskuM, SINGAPORE.
Weights: Fig. 1. 464 grams. (when intact). Fig. 2. 3164 grams.
GEOLOGICAL MAGAZINE NEW SERIES. DECADE Vik VO. INE 7 No. IV.—APRIL, 1916.
ORIGINAL ARTICLIEHS.
J.—Two rarer OBsIDIANITES FROM THE RaFriEs Museum, SIncAPoRE, AND NOW IN THE GeonocicaAL Department, F.M.S.
By J. B. ScRIvENOR, M.A., F.G.S. (PLATE VIL.)
OME years ago I was asked to look through a collection of geological specimens in the Raffles Museum, Singapore, and found in a drawer two exceptionally large obsidianites. ‘They were not labelled, and nothing could be ascertained about their history, but an assistant in the Museum said he thought they might have come from Kelantan, a State on the east coast of the peninsula. The weights of the two obsidianites were 464 and 316°4 grams. ‘The former and larger of the two was entrusted to a local firm to cut in half, with the result seen in Pl. VII, Fig.1. The photograph, nevertheless, shows that there is a group of vesicles in the centre. The photographs, which are natural size, also show that there is nothing unusual about the surface
of these specimens (Pl. VII, Fig. 2).
. An analysis of a portion of the larger specimen has been carried out by Mr. C. Salter, Chemist in the Geological Department, F.M.S. In May, 1915, Dr. Mueller (Gruoz. Mae., 1915, pp. 206-11) described under the name of ‘ Tektite’ obsidianites from near Tutong, a dismal, erocodile-infested station in Borneo that I also have had the misfortune to visit, and gave an analysis by Dr. Hinden (op. cit., p. 209). The close agreement in composition of the Singapore specimen is note- worthy, and is shown in the following table (p. 146), together with some of the analyses quoted in a recent paper by Mr. C. G. Thorp (‘‘A Contribution tothe Study of Australites,” Journ. W. Australian Nat. Hist. Soc., vol. v, pp. 1-26, 1914), and others of obsidian from Iddings’ Igneous Rocks, and from a description by Dr. Prior of rocks from British Kast Africa (‘‘ A Contribution to the Petrology of British East _ Africa,’ Min. Mag., xiii, pp. 245, 247, 1903). The more important constituents only are given, and the analyses of ‘ Australites’ and ‘Moldavites’ are selected from Mr. Thorp’s paper to show the extreme ranges of silica percentage. No. 12 is described by Dr. Prior as ‘‘phonolitic obsidian” ; No. 13 as ‘‘obsidian glassy soda-rhyolite”’.
The range in silica percentage in obsidianites is shown by the analysis to be large. Dr. Mueller mentions the difference in the composition of obsidianites from that of obsidians. There is certainly a marked difference compared with the U.S.A. obsidians, but when one compares them with the East African rocks, which differ chiefly in the preponderance of Na,O over K, 0, and considers that a glass
DECADE VI.—VOL. III.—NO. IY. 10
146
B. Smith—Ball or Pillow-form Rocks.
having the composition of some of the ‘ adamellites’ or ‘ granodiorites’ would have a composition even nearer that of the obsidianites, the
chemical difference that, I gather, Dr.
Mueller deems esas of
the obsidianites not being of terrestrial origin, does not appear to be A stronger objection to a terrestrial origin for
of great importance.
these Singapore specimens is ‘their weight.
Pumice from Krakatoa
OBSIDIANITES. OBSIDIAN.
2, i
a) Lies | British
ao 5 Australites. | Billitonites. | Moldavites. U.S.A. Hast
a5 3 Africa,
ne = :
_@)_|_Q) (8) (4) (5) (6) (7) (8) (9) (10) (@11)_}) (12) © as) Si Oo» 69-80)70-90|64- 68/77 - 72/70-92|71 - 14/77 - 69/82 - 68]75 -52)74- 52/76 - 20/64 -00/70-61 Ale Oz . |14-30/13-50/16-80|) 9-97/21-20/11-99)12-78) 9-56)14-11)13-72|13-17|10-43) 8-59 TiO,g .| 1-00) 1-00; — -86; — — = = = = == °78) -15 FeO .| 5-65) 5-47] 1-01) 3-75] 5-42) 5-29) 1-45) 1-13) -08 62 73| 3-86! 5-96 Fe, Oz . -15) -32| 6-57) -32)| 1-07) — | 2-05) — | 1-74) 1-01) -34] 6-30} 2-52 MnO .|trace|trace| -20/trace} -41} +32) — -18} — |trace| -10} -37| -34 Ca O 2-61) 2-35] 3-88) 2-40] 3-78] 2-84) 1-26) 2-06) -78| -78| . -42) 1-45) -61 MgO .| 3-20) 2-45} 2-50) 1-57) 2-61} 2-38] 1-15) 1-52) -10} -14) -19| -34) -07 NaoO .| 1-16) 1-46 trace] 1-29) 2-46) 2-45) -78| -63 3-92) 3-90) 4-31) 7-59] 6-77 KeO 1-90 2-17) 4-01) 1-96) 2-49) 2-76) 2-78) 2-28] 3-63] 4-02) 4-46) 4-59) 4-46
has floated to the east coast of the peninsula, but the idea of these obsidianites having floated to the peninsula attached to masses of pumice is precluded by the absence of any pumice of similar composition; and one cannot admit that bodies of this weight could drift in the upper atmosphere any more readily than one can admit it of arifle bullet. A cosmic origin seems the only possible explanation.
II.—Bat or Prttow-Frorm StRvucTURES IN SANDSTONES.?
By BERNARD SmiTH, M.A., F.G.S. fW\HE structures described below occur in monotonous and generally uninteresting type; namely in sandstones, interstratified with masses of shale and mudstone, exposed near the centre of the Berwyn Anticline in parts of Denbighshire. The necessity, however, of examining every exposure, incumbent upon the Surveyor, has led me to pay attention to detail, and especially to certain phenomena that would appear to be of world- wide occurrence in sediments of all ages. Description of the Sandstones.
The sandstones are of both Llandilo and Bala age. Those of Llandilo age occur sparingly in a mass of scantily fosellinerone shales in the Llanrhaiadr- ym-Mochnant district, but become more important when followed eastward along the strike in the direction of Llansilin. In the same districts the Bala Beds are more prevalently sandy, and the strata are of a more regular character.
1 With the permission of the Director of the Geological Survey.
rocks of a rather
_
B. Smith—Ball or Pillow-form Rocks. 147
1. Llandilo Sandstones.—In the west thick lenticles of sandstone, or masses of alternating lenticles and shales, occur at infrequent intervals, as at Llanrhaiadr, where one bed is as much as twenty feet in thickness. Farther east the beds of sandstone appear more frequently, and are often thicker than those in the overlying Bala, and sometimes of coarser type. They are well-developed near Moel y Gwelltyn, Gyrn Moelfre, Craig-yr-hwch, and Foel Rhiwlas.
The sandstones are blue laminated gritty quartz-felspathic and slightly calcareous rocks, often weathering like an ashy sediment; whilst some beds are true ‘ashy sandstones’. They contain pellets and pebbles of shale and mudstone, and in weathered specimens show brown or yellowish-red earthy inclusions. Like the Bala sandstones they contain white mica, which is clustered thickly along the ripple- marks. Although the prevalent type of rock is well-laminated, some of the coarser parts appear to be structureless. Drift- and current- bedding is fairly common. The constituent grains are angular and of two sizes, respectively about ;3>5 and 345 inch in diameter.
2. Bala Sandstones.—These occur normally as beds averaging about 2 feet in thickness, with interstratified shales and shaly sandstones. The thicker beds are nearer 3 feet across, but in some places, such as Nant Engyll Quarry, Coed Garth Eryr, Llwyn Bryn Dinas, and Llangedwyn Hall, lenticular masses, like those in the Llandilo, occur up to 10 feet in thickness.
¢ i Ra in, AG
Fic. 1.—Ball and pillow-form structures in beds of sandstone between cleaved shales, in crag west of Moelfre, Llansilin.
When fresh the rocks are tough, blue, or blue-grey, fine-grained laminated micaceous sandstones, with many included lamine of shale. They are fossiliferous and occasionally slightly calcareous, when they weather to rottenstone. Frequently they are ripple-marked and show drift- and current-bedding, the latter structure being most common in the more lenticular masses. They are less felspathic than the Llandilo sandstones, but contain some thin layers of ash and isolated crystals of felspar.
Pillow-form and Ball Structures.
In some sections, either natural or quarried, parts of the sand- stone, interbedded either in similar sandstone or in shale, assume
148 B. Smith—-Ball or Pillow-form Rocks.
a pillow-form (Fig. 1), ball-like, or semi-spheroidal habit. The spherical contours are usually developed on the undersides of projecting ledges of weathered sandstone as rounded lobes and curved surfaces, whilst occasionally they occur on the upper surfaces as well, when the rock becomes still more pillow-form in appearance. The spheroids are hardly ever completely developed. If they were they would average about 1 foot in diameter, with a maximum of 2 ft. 6in.
The pillow-form shapes are sometimes arranged parallel to the bed,’
but are frequently inclined. They are often twice as long as thick, and average from one to two feet in length.
Externally the shapes of these masses recalled those of pillow- lavas, or the spheroidal weathering of dolerite, and since some of the pillows contained much felspathic material and some of the spheroids appeared to be due to weathering, their occurrence was sufficiently interesting to warrant further investigation, which showed that they were of two kinds.
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LAA
Wits iN vi
‘
Fig. 2.—Shell-jointing in sandstone.
Two Types of Structure. 1. Structures due to jointing and weathering (shell-jointing). 2. Pillow-form or ball structures due to internal build.
1. Where the rocks are evenly bedded and well jointed the corners of roughly rectangular masses, blocked out by joints and planes of stratification, are liable to shell off in layers roughly concentric with the central portions of the blocks. As in dolerite the shell structure may be due primarily to shrinkage. In undoubted cases (Fig. 2 where this shelling off takes place ' the fracture was unrelated to the lamination, which runs normally through the pillow. The exposed top corners of a block are usually shelled off first, unless the lower corners project prominently from the underlying beds. On hammering at such a pillow the concentric weathered shells may be knocked off in turn until only the tough unweathered core remains.
2. In other cases, if we hammer at a pillow or spheroidal mass we discover that its internal structure may correspond with its curved face; that is to say, the lamine of sandstone are curved in conformity with the outer curve of the pillow. A good example occurs in an old quarry in Llwyn Bryn Dinas Wood, about one mile west of Llangedwyn. Some of the sandstone strata are evenly bedded and
1 For this reason the rock is unsuitable for use in the exposed corners and angles of buildings. It is known locally as ‘ grinsel’.
ee ee
B. Smth—Ball or Pillow-form Rocks. 149
apparently quite undisturbed, whilst others (Fig. 3) have ball structures strongly developed and exposed chiefly, be it noted, on their under surfaces. Where these surfaces curve upwards until they are nearly, or more than, at right angles to the normal plane of stratification, the sandstone laminz curve upwards and over, in conformity with them. In one or two places shales are plastered against the curved surfaces as if squeezed into spaces between the spheroids.
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Fic. 3.—Ball structures in sandstone, Llwyn Bryn Dinas Wood, Llangedwyn.
This example seemed to furnish conclusive evidence in favour of the balls or spheroids being due to internal concentric lamination, yet the next time I came across semi-spheroidal masses their curved surfaces
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3.8.
Fie. 4.—Sandstone ‘ ball’, Tyddyn-main, Llansilin.
were due, quite as conclusively, to jointing and weathering. How- ever, many cases of the real thing were quickly forthcoming, and T have since found that true ball structures are quite as common as, if not more common than, the rounded masses due to shelling.
150 B. Smith—Ball or Pillow-form Rocks.
Other examples occurred (i) in a quarry between the road and river east of Coed Fron-fraith; (ii) in a quarry about 200 yards west of Tyddyn-main; (ili) in a quarry at l'yn-y-ffridd in ashy sandstone, where shales are pinched in between two balls; (iv) on Moel y Gwelltyn, where the balls are from 18 inches to 2 feet in thickness ; (v) in the crags west of, and overlooking, Moelfre (Fig. 1); (vi) in a quarry south of Pant-er-eos-uchaf; (vil) in numerous quarries and crags between Moelfre Hall and Moeliwrch on Gyrn Moelfre.
In some cases it is possible to study sections of the ball structures on joint faces where the lamination has been rendered visible by weathering. In a quarry about 200 yards west of Tyddyn-main (ii above, Fig. 4) a flat broken surface of a ball, in a big lenticle of sandstone, reveals its internal structure, for the exposed lamine are curved back upon themselves in a sharp fold, to which the outer curve of the ball conforms.
~
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a)
Fic. 5.—-Contorted layers in sandstone near Pentre, Llansilin.
A better section is visible in an old quarry in a wood 200 yards east of Pentre, on a nearly vertical joint face which runs approxi- mately in the direction of the dip (Fig. 5). It shows a well-laminated and slightly drift-bedded sandstone, in which some of the laminze (about 12-15 to the inch) are strongly contorted, folded back upon themselves, and cut off from other parts of the rock by faults. The rounded ends of these curved masses are often buried in apparently structureless sandstone, whilst the disturbed horizon is both underlain and overlain by normally bedded sandstone. At some future date the balls will be developed by differential weathering of the structureless parts of the rock.
B. Smith—Ball or Pillow-form Rocks. 151
Cause of Contortion.
Anything more unlike concretionary action could hardly be
imagined. To what, then, must these structures be attributed ? ’ TIT can imagine no means that would avail to turn over, and break up, layers of sediment on this scale—sandwiched between normally bedded identical layers of identically similar sandstone‘—after the higher layers had been deposited. Movements during consolidation, due to differences in composition, cannot be invoked, because there is _ no difference in composition. Nor can we appeal to cleavage-stresses, although in some cases, discussed below, they may have achieved something of a secondary order.
There remains to find some means whereby the sediment could have been disturbed before the higher undisturbed layers were deposited. Two agencies are possible: either (1) packing or sliding movements on gentle slopes owing to irregularity of deposition and gravitational
-ereep, or (2) movements of overlying bodies of water as tidal or ocean currents.
Nature of the Movements.
The highly lenticular character of these beds has already been emphasized, and the examples figured show how the rock was drift- bedded and ripple-marked during deposition. Nothing is more obvious than that the sediment was transported by currents and laid down sporadically in fairly shallow water, layers of mud being frequently interspersed between layers of sand and silt. From these facts we may safely infer that the sea-bed was gently undulating. Again, the sediments were apparently formed off the shores of volcanic islands drained by rivers carrying ashy and other sediment to the sea, which would be agitated periodically by strong tidal currents. The large voleanic bombs and lumps of shale in the Bala ashes would seem to prove that the volcanoes rose above the water, for the bombs could not have been cast far from the vents had the latter been submarine.
Most of the sediment had apparently reached a state of pasty semi- consolidation that allowed of overfolding and thrusting within its mass, but its upper layers were still so incoherent that they could be stirred up and easily rendered structureless.
A lenticle of sandstone, deposited on a gentle slope, might find itself in a state of unstable equilibrium through gravitation alone, which would set up a tendency to creep and internal readjustment. Furthermore, the edges of a lenticle deposited on a slope of mud would tend to break up and have its detached fragments incorporated in the enveloping mud.
It is well-known how Glacial and post-Glacial gravels, resting on gentle inclines, have become contorted by gravitational creep. A mass of laminated sandstone under water would be an even more likely subject for this operation, which might be started or accentuated by tidal movements, or the sweep of changeable ocean currents.
1 Contrast ‘ mud-lumps’, where mud is squeezed out from between sand- stones that are of different composition and grade of material (see later, p. 155).
152 B. Smith—Ball or Pillow-form Rocks.
Current Action.
The disturbing effects of current-action can indeed be demonstrated ; for semi-rounded lumps of sandstone (1-2inches across, in Llwyn Bryn Dinas Wood) occur in the shales lying between the thicker lenticles of sandstone, as if thin layers had been deposited and subsequently broken up, rolled along, and embedded in the mud. Conversely, the thicker sandstones contain little strips, angular pellets, or rounded pebbles of mudstone—proving without doubt that the beds were frequently torn up when they had barely attained a state of consolidation.
We may compare such destructive current-action with that to which I ascribe the contortions in the dolomitic sandstones in the Keuper Marl of Nottinghamshire.’ In this connexion also, the occurrence of structureless sandstone in which the balls or pillows are embedded is suggestive.
Thus, although I am not an advocate of the efficacy of current- action to form the large ball structures met with in these Paleozoic sandstones, but prefer to think they are chiefly due to gravitational creep in lenticular beds, I am of the opinion that currents have played a greater part in aiding such movements than some geologists might admit.
Effects of Cleavage.
The effects of cleavage may now be considered. During the process of shearing and compression that induced cleavage the irregular lenticles of sandstone acted as resistant cores or sheets, and only yielded to the impressed forces after a struggle. In some cases they slid bodily through the shales, which were caused to flow round them like so much butter; in other cases they were bent and folded ; whilst in others, again, they were faulted or broken into small masses—like the quartz veins in the Ilfracombe slates. The latter condition is so common that it is inadvisable to rely upon a dip taken in any small isolated mass of banded sandstone, for I have frequently found the true dip of the enclosing shales to be almost at mght angles to that of the broken lenticle.
When the sandstones occur as large lenticles or clusters, the boundaries of the mass, or group, are often faulted, and the combination buckled into folds—structures which may be further complicated by post-cleavage movements. The shaly portions of the combination are frequently cleaved, whilst at other times the sandstones are cleaved as well. In the latter case the angle of cleavage in the sandstones is invariably higher than it is in the shales: an effect that would seem to imply that the thickness of the shale-belts, relative to that of the sandstones, has been decreased by cleavage-shear, and that the higher beds of sandstone have moved further than those below.
In the heart of a thick mass of sandstone cleavage has had little or no effect upon the relations of the ball structures to their surroundings ; but where they occur at the margin of a lenticle (a very likely position) and where lumps of sandstone in the first instance have been detached
1 “The Upper Keuper Sandstones of East Nottinghamshire ’’?: GEOL. MAG., 1910, pp. 302-11. i
B. Smith—Ball or Pillow-form Rocks. 153
and isolated in the shales, the effect of the cleavage has been to jam these lenticle-noses or semi-rounded balls into the shales, which were thereby slickensided and plastered tightly upon them. Insome cases, indeed, a sort of subsidiary cleavage (due to jamming) curves round the balls in places where the ordinary cleavage had little effect.
Fic. 6.—Diagram showing curved cleavage.
A local curved cleavage, developed in this definite manner, may either accentuate the true ball structures, or suggest ball structures even when the sandstone lamine do not conform to the curved surface. Fig. 6 is an attempt to express these two cases diagrammatically.
Similar effects are liable to occur also on a large scale about masses of sandstone and shale 100—200 feet in thickness, the slickensides being represented by faults. In the lee of the mass we may find (taking the analogy from a ‘rain-shadow’) a ‘cleavage-shadow ’, or locality in which the cleavage is modified or absent owing to the protection afforded by the sandstone.
Some allied phenomena.
Amongst allied phenomena we might instance the contortions and uneven deposition of some of the Wenlock—Ludlow beds of Denbigh- shire. These consist chiefly of blue shales with sandy laminz which become clustered at frequent intervals to form sandy shales or thin beds of sandstone. The clusters are usually only half an inch or so in thickness, but some of the sandy beds may attain a maximum of 6-8 inches. Occasionally the sandy beds are split up by muddy
Se * ee ee a ree € Ins Se
Fic. 7.—Folded layers of sandstone and shale, Pant-yr-onn, Llanelidan.
layers. In one case, near Pant-yr-onn, Llanelidan, an 8 in. band of laminated sandstone contained 6-7 muddy layers, those near the centre of the bed being thrown into gentle undulations, of wave- length about 9 inches and amplitude about 3 inches, whilst the upper and lower layers pursue a straight course (Fig. 7). Here and there the folded bands of mudstone thicken quite suddenly, especially on
154 B. Smith—Ball or Pillow-form Rocks.
the crests of the small anticlines. Had the folding been due to packing caused by cleavage-stresses the whole bed would have folded, instead of only the middle portion. The most likely explanation to account for the facts is that the composite bed was deposited on a slight slope, and a creeping movement was set up, whilst the layers were still soft, causing the bed to become undulose internally, and to thicken at the same time. The top and bottom of the bed would remain relatively undisturbed, but each individual layer of sandstone, between the little layers of mud in the middle of the group, would move slightly in the direction of the creep.
Signs of current-action and uneven deposition are common in these beds. In the quarry south-south-west of Nant Gaer, near Bryn Eglwys, there is a 6in. band of slightly calcareous and fossiliferous laminated sandstone with uneven upper and lower surfaces. The upper has flowing curves which correspond roughly with the surfaces of the ripple-marks, whilst the lower is much more irregular, for the sandstone fills up little pockets that either have been torn out of the mud by current-action, or have been formed by the lowest sand- stone lamin buckling downwards whilst in a pasty state. ‘The higher rippled lamine of sandstone truncate this lower pocket-filling set (Fig. 8).
Fig. 8.—Sandstone in shale, Nant Gaer, near Bryn, Kglwys.
Most of this effect, as in the case of the Keuper ‘skerries’ of Nottinghamshire, I should attribute to current-action,’ for the wave- length and amplitude of the ripples agree very closely with those proper for sandstones of this type, as worked out by Sorby.? The occurrence is altogether different from that shown in Fig. 7.
Conclusion.
Ball or pillow-form structures in sandstones, and certain bucklings and foldings, seem to be most satisfactorily explained on the assumption that they are primarily due to internal readjustments of freshly and unevenly deposited sediments, acting mainly under gravitation. These readjustments may be aided, or started, by the action of strong currents.
The above-mentioned structures and their attendant phenomena are not confined to Paleozoic sandstones,* but must occur frequently in
1 “The Upper Keuper Sandstones of Hast Nottinghamshire ’’: GEOL. MAG., 1910, pp. 306-7.
2 “On the application of Quantitative Methods to the Study of Rocks’’: Q.J.G.S., vol. lxiv, pp. 171-233, 1908.
* I have recently seen ball structures in the sandstone of St. Bees Head, Cumberland, and Dr. R. lL. Sherlock tells me that pillow-form masses of Magnesian Limestone overlie puckered Marl Slate in a cutting at the north end of Annesley Tunnel in Nottinghamshire.
3 . » - aa 8 ee EE
B. Snuth—Ball or Pillow-form Rocks. 155
the Mesozoic and Tertiary rocks, especially the latter. I am not aware, however, that much attention has been paid to them, although I am convinced that a strict examination of ripple-marks, current- and drift-bedding, internal creeping-movements, and removal of sediment by current-action would yield important results if studied in conjunction with present-day sedimentation in, and beyond, the mouth of one of our great tidal estuaries.
We want to know, for example, the extreme depth at which ripple- marks can be formed, and to what extent depth is a deciding factor. We require reliable data as to the rate at which sandy sediment may be accumulated and again removed by current-action; the relative effects of a flood- and ebb-tide on sedimentation; and if a layer of drift- or current-bedded sand is laid down by the one, how far it may be wiped out by the other, or covered up by further sediment. When we find the lamin of false-bedding or ripple-drift (in a rock exposure) dipping in a certain direction, are we to assume that the sediment was carried directly to that spot from the land? These and similar questions may be difficult to solve, but would give scope to an investigator provided with a suitable boat, and ample leisure for the task.
Tae Misstsstppr Detra.
Since writing the above it has been my good fortune to light upon an instructive paper dealing with the conditions obtaining in the region of the Mississippi Delta.' Investigations were undertaken with the object of discovering the nature and mode of formation of the mud-lumps that obstruct the navigation at the river mouths. The results achieved, although they have not fully settled the origin of the mud-lumps, are enlightening.
It has been shown, for example, that the deposits near the mouth of the river consist of lenticular layers of dark-blue clay, fine sand, and silt, and a great many beds of intermediate character, each of which grades into the adjacent beds. The sandy beds, and those of mixed sand and clay, are much more rigid than nearly pure clay. The most rigid material is a mixture of sand and clay in certain definite proportions, whilst some of the clays are very fluid. The resemblance between these deposits and some of those of Ordovician and Silurian age, as they would have been at the time of their formation, is striking; although this, of course, does not imply that the Lower Palzeozoic deposits were of deltaic origin.
Just off-shore, and adjacent to the mouths of the river, silt is accumulating at the rate of several inches a year, and the character of the deposit varies from season to season. uring high-water—the first half of the year—the sediment is coarser than during the low- water period. The apparent result is astructure somewhat resembling the annual rings of growth of trees. This is a suggestive fact, if we bear in mind the sequence of sedimentation of some of the older rocks, in e.g. the Wenlock—Ludlow Series (see p. 153).
Again, certain features of the Delta suggest that it is affected by a process of bodily flowage towards the sea, giving rise to readjustment
1 The mud-lumps at the mouths of the Mississippi, by E. W. Shaw, U.S.G.S., Professional Paper 85-8, 1913.
156 Dr. C. 8. Du Riche Preller—Prietre Verdi.
between the more or less resistant layers of sediment, both in the Delta itself and in the sea-bottom just off-shore.! The surface of the deltaic deposits is also subsiding, the subsidence being most rapid where the Delta is growing most rapidly; and the material is presumably becoming more compact and losing its very watery condition. These, again, are significant facts, and bear directly upon the subject of this communication. We have at once a clue to much that was pure surmise—the unstable relations of these sandy, silty, and clayey deposits to one another, and the comparative rigidity of some of the more sandy beds, which would allow of thrusting and buckling within them, although they were still in a pasty condition.
Il].—Taue “ Prerre Verpr’’ or tHE PifmMontrEsE ALPS. By C. S. Du RIcHE PRELLER, M.A., Ph.D., M.I.E.E., F.G.S8., F.R.S.H.
N a previous paper on the Permian Formation in the Alps of Piémont, Dauphiné, and Savoy,? I referred incidentally to the large masses of pietre verdi or greenstones which constitute perhaps the most striking geological feature of the extensive areas covered by the crystalline rocks of the Piémontese Alps in a crescent-shaped curve about 200 miles in length from the Maritime range to Monte Viso, Grand Paradiso, and Monte Rosa. In the present paper I propose to deal more fully, although necessarily within narrow limits, with these pietre verdi which, owing alike to their extraordinary development, variety, and complexity, to their intimate association with each other and with the crystalline sedimentary rocks, and to their intricate composition and origin, have for the last fifty years presented most interesting problems and passed through many remarkable phases of interpretation. As a necessary preliminary to a description of the different areas, it will be convenient to briefly consider the most recent classification of the crystalline formations of the Piémontese Alps generally, and of the pietre verdi rocks in particular.
I. CLAssIFICATION OF THE CRYSTALLINE FoRMATIONS.
In a short paragraph of the previous paper already quoted, I outlined the sequence of the crystalline rocks of the Piémontese Alps as evolved by Zaccagna in his revealing memoirs of 1887 and 1892.8 In this classification he retained Gastaldi’s two principal pre-Paleozoic zones or horizons,‘ but with this essential difference, that for Gastaldi’s upper or so-called pietre verdi zone he substituted
1 The mud in the ‘lumps’ is supposed to be squeezed out from between the sandy beds.
2 GEOL. MAG., January, 1916, p. 7; ibid., p. 15.
3D. Zaccagna, ‘Studi geol. sulle Alpi Occid.’’: Boll. R. Com. geol. d’It., 1887, p. 346 et seq. ‘‘Riassunto di Osserv. sul Versante Occid. Alpi Graje’’: ibid., 1892, p. 175 et seq.
4 B. Gastaldi, ‘‘ Studi geol. sulle Alpi Occid.’’?: Mem. R..Com. geol. d’It., 1871, vol. i, p. 3 et seq. ‘‘ Spaccato geol. lungo le valli sup. Po e Varaita’’ : Boll. R. Com. geol., 1876, p. 104 et seq.
Dr. C.S. Dw Riche Preller—Pietre Verdi. 157
the mica-and-cale schist zone with pietre verdi as associated rocks, the latter being, in point of superficial area, a subordinate, the former the predominant part of the whole formation. Zaccagna’s two Archean zones thus comprised: (1) a lower one, restricted exclusively to primitive gneiss and granite without pietre verdi; and (2) an upper one, graduating, in ascending order, from minute and tabular gneiss to mica-schists and cale-schists, each group with crystalline limestone and pietre verdi. This classification, in its logical sequence and convincing simplicity, received the imprimatur of the Italian Geological Survey under its eminent Director, the late Comm. F. Giordano,’ and was also accepted by the French Survey, by Bertrand, Termier, and other French geologists. It derived additional force from the more intense metamorphism and crystallinity, pro- gressing from west to east, of the rocks on the Piémontese as compared with those on the French side of the Western Alps; and this, together with the fact that until then, about 1890, no deter- minable fossils had been found even in the uppermost calc-schist horizon, warranted the entire crystalline series of Piémont being classed as of pre-Carboniferous, and, in the absence of the lower Paleozoic, of Archean age.
But in 1894 Bertrand returned to his former view of the Mesozoic age of the schistes lustrés which, in opposition to the late Professor Lory’s Triassic and to Zaccagna’s Archean views, he and Termier had already pronounced Liassic in the well-known case of Mont Jovet in Tarantaise (Isére Valley). In his Etudes dans les Alpes Frangaises * Bertrand maintained the Liassic age of the calc-schists not only on the French but also on the Italian side, on the ground that lower Triassic masses frequently underlie the calc-schists. Even before the publication of that work, Professor Parona, of Turin, had discovered Radiolaria in the silico-calcareous mass associated with the cale-schists and pietre verdi (serpentine) of Mont Cruzeau, near Cesana,* a discovery followed a few years later by other evidence of characteristic Liassic, Rhetian, and Triassic fossils in the dolomitic and caleareous masses which, in the lower as well as in the upper valleys of both Southern and Northern Piémont, occur at varying levels of the cale-schist horizon, either resting on, or intercalated between, or in some cases at the base of, the crystalline calc-schist strata. These discoveries were due chiefly to the untiring industry and perseverance of Franchi, who, in two important memoirs of 1898 and 1904,° claimed to have established the Mesozoic,
1 Boll. R. Com. geol., 1887, pp. 342-5.
2p. Termier, ‘‘ Sur le Permien du massif de la Vanoise’’: Bull. Soc. géol. France, vol. xxi, p. 124 et seq., 1893.
3 M. Bertrand, Bull. Soc. géol. France, vol. xxii, p. 69 et seq., 1894.
“cC. F. Parona, ‘‘Sugli Scisti silicei a radiolarie di Cesana presso il Monginevra’’: Atti R. Ace. Sc. Torino, vol. xxvii, 17. Gennajo, 1892; also noticed in Davies & Gregory’s paper on ‘‘ The Geology of Mont Chaberton ’’, Q.J.G.S., 1894, p. 303 et seq.
° §. Franchi, ‘‘ Sull’ et& mesozoica della zona delle pietre verdi nelle Alpi Occidentali’’: Boll. R. Com. geol., 1898, pp. 173, 325 et seq. ‘‘ Ancora sull’eta mesozoica, etce.’’: ibid., p. 125 et seq. Franchi, Novarese, and Stella were in charge of the detailed survey of the Piémontese Alps forthe new1:100,000 map in
158 Dr. CO. S. Du Riche Preller—Pretre Verdi.
and more especially the predominantly Liassic, age of the cale-schist formation, including in the same the pietre verdi as associated rocks. He thus assimilated the age of that formation and that of the schistes lustrés in accordance with Bertrand’s views, with which he is thoroughly imbued and which, since Bertrand’s death, have been upheld and even carried considerably further by Termier. Franchi’s memoirs and his evolution from the Archean to the Mesozoic led to a controversy as interesting as it was vigorous and protracted, between Zaccagna and himself, not as to the facts, which were not in dispute, but as to the interpretation of the same. ‘'o Franchi’s contention Zaccagna' opposed, on stratigraphical grounds, his own explanation that the fossiliferous calcareous and dolomitic deposits occur in eroded gaps and as squeezed wedges (przsicature) in the crystalline cale-schists, in which they were infolded by dynamic action, in certain cases by displacements due to local overthrusts, and that as such they are quite distinct from the true cale-schists, whose pre-Palwozoic age he therefore strenuously reaffirmed.2? In the result Professor Taramelli, of Pavia, and Professor Parona, of Turin, as referees appointed by the Geological Survey, recommended, in their reasoned report of 1911,° that for the purposes of the new large-scale map 1: 100,000 of the Piémontese Alps, Franchi’s interpretation, as being, in their view, more con- vincing and up-to-date, should be adopted, but with the explicit and judicious reservation that the question cannot be considered settled but remains open; that at a lower horizon there may be cale-schists
conjunction with Mattirolo, who supported Zaccagna’s interpretation. Franchi published in Boll. R. Com. geol., 1909, p. 252, a forty-page reference of the literature on the crystalline schists from Gastaldi (1871) downwards.
The principal localities which yielded Triassic and Liassic fossils in the calcareous and dolomitic masses of the calc-schist horizon are the Grana, Narbone, Maira, Elva, and Varaita Valleys in Southern Piémont; Chianoc in the lower, and Rocca d’Ambin, Gad d’Oulx, and Bardonecchia in the upper Susa Valley; Villeneuve in the upper Aosta Valley, and the Col du Petit St. Bernard, all in Northern Piémont. The fossils, most of which were determined by Professor Di Stefano and Professor Canavari, include, among others, Radiolaria, Belemnites, Arietites, Crinoids, Hncrinus, Pleurotomaria, Avicula, Corallari, Gyropelle, Pentacrinus, Phylloceras, etc.
1D. Zaceagna, ‘‘Osservazioni sugli ultimi lavori intorno alle Alpi Occidentali’’: Boll. Com. geol., 1901, pp. 4, 129; 1902, p. 149; 1903, p. 297.
2 Zaccagna’s interpretation agrees with Professor Bonney’s view that nothing is more common in the Alps than Jurassic and Triassic wedges in the crystalline schists. ‘‘ Mesozoic Rocks and Crystalline Schists in the Lepontine Alps’’: Q.J.G.S., 1894, p. 285; also ibid., p. 277. Baretti (Studi Gran Paradiso, etc., 1876-7) also considered the French calc-schists the upper and the Piémontese calc-schists as the lower crystalline formation.
3'T. Taramelli and C. F. Parona, ‘‘ Relazione sull’et& da assegnarsi alla zona delle pietre verdi nella Carta geol. delle Alpi Occidentali’’: Boll. R. Com. geol., 1911, pp. x-xxiv. The controversy between Franchi and Zaccagna turned more especially on the great calc-schist area extending from the Gesso Valley in Southern Piémont parallel to the Franco-Italian frontier to the Susa and Aosta Valleys towards Monte Rosa. ‘The smaller, isolated area of Courmayeur, running parallel to Mont Blanc, was recognized as Liassic and Triassic, and was, therefore, not in dispute.
Dr. 0. S. Du Riche Preller—Pietre Verdi. 159
in Zaccagna’s sense; and that the Piémontese Alps, in their elusive
complexity, may J vet reveal the most sur prising phenomena just when
the problem of the crystalline schists and pietre verdi appears to have _been solved.
Thus, in the most recent Italian Geological Survey map 1: 100,000, as also in the one of 1 : 400,000 of 1904, the Piémontese cale-schist formation has been rejuvenated as equivalent to and contemporaneous with the schistes lustrés of the French, the Biindnerschiefer of the Swiss, and the Schieferhiille of the Austrian Alps. It figures,. therefore, as the Liassic—T'riassic crystalline ‘‘ Piémontese”’ facies, with two subordinate facies—the ‘‘ mixed ”’ and the “‘ ordinary ”’ Trias. This rejuvenation, which is practically a reversion, mutatis mutandis, to Sismonda’s ‘‘ metamorphosed Jurassic schists ” of the early ’ sixties, entailed a similar stratigraphical process as regards the mica-schists and the minute, tabular, and graphitic gneisses which, accordingly, are now assigned to the Permo-Carboniferous, corresponding to Bertrand’s and Termier’s ‘‘série cristallophylienne permo-carbonifére’”’. The only formation left to the Pre-Carboniferous (or Pre- Paleozoic) is therefore that of the primitive gneiss belt of the Mercantour, Maira-Dora, and Gran Paradiso massifs, which formation constitutes the practically undisturbed substratum of all the more recent series.!
This primitive gneiss, often of granitoid and porphyroid structure with large felspar crystals up to 8 centimetres in length, differs lithologically from the more recent minute and tabular gneiss, chiefly in that the small-grained elements of the latter are conspicuously rich in quartz and predominantly white mica. As regards the calc- schists, they are composed prevalently of calcite, aggregations of quartz in minute granules, and with white or greenish mica, the rock being generally of grey and often blackish colour due to a carbonaceous pigment, with numerous minute crystals of pyrite and other metallic minerals. When this typical cale-schist is deficient in calcite or loses it altogether, it assumes an essentially phyllitic character; when, on the other hand, calcite predominates over the other minerals, the calc-schist. becomes micaceous crystalline limestone or ‘calcefiro’?; and when the crystalline limestone is, by contact, impregnated with serpentinous matter, it becomes ‘ophicalce’, as e.g. the green marble of Susa.
1 The official geological map of France, 1: 1,000,000, published in 1904, which extends to the Italian side as far as the Po Valley, includes in the Permo-Carboniferous not only the minute and tabular gneiss and mica-schists, but also the primitive gneiss belt, for which there is no warrant. Similarly, Termier (‘‘ Les schistes cristallins des Alpes occidentales,’’ Comptes Rendus du Congrés géol. Vienne, 1913) embraces in his série cristallo-phylienne triassique compréhensive all the younger formations down to the Eocene inclusive. Both cases are ultra-synthetic, and are not accepted by the Italian Survey.
Professor Gregory’s view that the gneisses which he terms Waldensian (Q.J.G.S., 1894, p. 232 et seq.) are Pliocene and intrusive runs counter to the accepted interpretation of the coarse-grained gneiss being the primitive, viz. ‘fundamental’, substratum of the Cottian and Grajan Alps. Professor Gregory’s conclusions are traversed also by Novarese, ‘‘ Rilevamento geol. Valle Germanesca (Alpi Cozie), 1894,’’ Boll. R. Com. geol., 1895, p. 277 et seq., and Franchi, ibid., 1897, p. 13 et seq.
160 Dr. C. 8S. Du Riche Preller—Pietre Verdi.
The new classification, besides harmonizing with the most recent interpretations west and north of the Alps, has the signal advantage of having eliminated Gastaldi’s ‘‘ pietre verdi zone”, which, in his separate and far too comprehensive sense, had become a fruitful source of misconception. As experience has shown, pietre verdi are not peculiar to any particular horizon, and throughout Italy, as elsewhere, occur in all the formations from the Hocene down to the Paleozoic; in the Piémontese Alps, though in a special form, even in the primitive gneiss.
II. CLAssIFICATION OF THE PIETRE VERDI.
In order to avoid tedious repetition, it will be convenient to specify briefly the leading varieties of the pietre verdi, some of which have characteristics peculiar to the Piémontese Alps. Gastaldi, with his wonderful intuition and perspicacity, laid down certain broad lithological distinctions which, in the main, are still correct. They were used by hisimmediate contemporary followers Striiver and Baretti, and after them by Bucca,’ in their excellent and diffuse macroscopic and microscopic investigations, and until recently also by Zaccagna and Mattirolo; but the results of the detailed survey and the consequent extension of microscopic work, notably by Franchi, Novarese, and Stella, have led to revised and more precise definitions, more especially in reference to the amphibolic and prasinitic series which Gastaldi included indiscriminately in his ‘amphibolic’ or ‘“magnesian schist zone’.
On the rational ground that not amphibole, i.e. hornblende, but triclinic felspar is the most prevalent constituent of pietre verdi, the revised nomenclature divides all the basic rocks of the Piémontese Alps into three groups on a felspathic basis, viz. rocks in which felspar, as a constituent element, is essential, subordinate, or absent. In the following table I have enumerated only the principal, most diffused rocks, without their schists, their infinite graduations, and their often overlapping varieties and combinations.’ .
PIETRE VERDI ROCKS.
I. Rocks with primitive elements.
(1) Essential. Diorite, diabase, porphyrite, gabbro, and their FELSPAR varieties.
(2) Subordinate. Felspathic lherzolite, felspathic hornblendite.
(3) Absent. Lherzolite and peridotite, hornblendite.
1 G. Striiver, ‘‘Cenni sui graniti massicci delle Alpi Piémontesi e sui minerali delle valli di Lanzo’’: Mem. descr. Carta geol. d’Italia, 1871, p. 37 ef seq. M. Baretti, ‘‘ Studi geol. sul gruppo del Gran Paradiso’’?: Mem. Acc. Lincei Torino, vol. i, p. 197 et seq., 1876-7. L. Bucca, “‘ Appunti petrogr. sul gruppo del Gran Paradiso’’: Boll. R. Com. geol., 1886, p. 449 eti seq.
2 The table is founded on the nomenclature worked out by Novarese and Franchi, Boll. R. Com. geol., 1895, p. 164 et seq. and p. 181 et seq.; but I have arranged it somewhat differently so as to group the rocks with primitive and those with secondary elements separately and more prominently.
Dr. 0. 8. Du Riche Preller—Pietre Verdi. 161
II. Rocks with secondary elements.
(1) Essential. (a) Prasinite group: with a dominant non- felspathic element, viz. chloritic, amphi- bolic (actinolite and glaucophane), or epidotic prasinite, and varieties.
(6) Euphodite and its varieties.
(2) Subordinate. (a) Amphibolite group: felspathic and epidotic amphibolite with frequent glaucophane.
(6) Epidotites and zoisitites, felspathic.
(a) Amphibolite group: epidotic and garnetiferous amphibolite with dominant glaucophane, eclogite.
(6) Epidotite, zoisitite.
(c) Serpentine, serpentinous, chloritic, and talcose
schist.
FELSPAR (3) Absent.
It will be seen that the old generic group of amphibolites or hornblendic rocks is separated into amphibolites proper and prasinites, the last-named designation having been adopted from Kalkowsky and Zirkel as basic rocks or ‘Griineschiefer’ of a felspathic basis with chlorite, hornblende (the bright-green actinolite or the bluish-green or violet fibrous glaucophane) and epidote, one of these being dominant as a non-felspathic element. The amphibolites, largely derived from diorite and composed of albite, epidote, and dominant amphibole, are mostly compact, passing to schistose, although the hardest, massive amphibolite, viz. ‘hornblendite’ or ‘ Hornblendefels’, is, in large masses, comparatively rare in the Piémontese Alps. The prasinites, on the other hand, are on the whole less compact and more often schistose, and in the main, like the amphibolites, altered, transformed, or metamorphosed from massive eruptive rocks. They often contain, as an accessory mineral, white mica, but rarely biotite, and include, as a largely diffused variety, the chloritic rock ‘ovardite’, first recognized and so named by Striiver’ from Torre d@Ovarda, a ridge in one of the three Stura di Lanzo valleys. It is composed of epidote, microscopic amphibole, and predominant chlorite in a plagioclase groundmass. Amphibolic schist, the equivalent of ‘ Hornblendeschiefer’, is intermediate between amphibolites proper and prasinites.?
A further distinction made is that between gabbro and euphodite in the sense that gabbro is restricted to the primary eruptive rock with its elements unaltered, while in euphodite the triclinic felspar is already altered to saussurite and the diallage to smaragdite—the latter being, like epidote and the amphibole varieties, a largely diffused mineral in the Piémontese Alps.
Again, massive serpentine, as the direct product of altered lherzolite and peridotite, is distinct serpentine schist, which is a further
1 Striiver, Una Salita alle Torre d’Ovarda, Torino, 1873, and Bucca, loc. cit., 1886, p. 453.
2 The felspar-actinolitic rock noticed by Professor Bonney near Fenestrelle in the Chisone Valley (‘‘ Two Traverses of the Crystalline Rocks of the Alps”’ : Q.J.G.S., 1889, p. 80 et seq.) is an amphibolic prasinite, viz. ovardite, while the schist with glaucophane, the epidiorite, and the dark-green porphyrite mentioned by Professor Gregory in his ‘‘ Waldensian Gneisses’’, loc. cit., come under the category of prasinites (ovardites) and amphibolites.
DECADE VI.—VOL. III.—NO. IY. 11
162 Dr. C. S. Du Riche Preller—Pretre Verdt.
stage of alteration, and still more from serpentinous schist, which, occurring frequently as intermediate between crystalline schists or, again, between crystalline limestone and pietre verdi, is the product of chloritic decomposition of the latter. As such it may, by the abstraction of magnesia, be derived from any of the basic rocks with altered elements, notably from euphodite, amphibolite, and prasinite, or their schists, although the prototypes of these rocks—gabbro, diorite, and diabase—hayve, apparently, no identity of origin or affinity with serpentine proper. So-called serpentinous schist is therefore pseudo-serpentine, and represents, together with chloritic and talcose schist, probably the last stage of alteration and metamorphism, not only of serpentine but of some of the other pietre verdi series,
The rocks with altered elements often assume a laminated, gneissi- ' form structure, and exhibit a marked affinity with gneiss or, again, with mica-schists and even with calc-schists. Thus minute eneiss becomes amphibolic, prasinitic, or epidotic ; mica-schist becomes epidotic and even more frequently glaucophanic when in association with the blue glaucophane or gastaldite variety; while ovardite, when very rich in chlorite and taking up mica, quartz, and calcite, passes into prasinitic cale-schist and phyllite.
The massive eruptive rocks with primitive elements—diorite, diabase, gabbro, pyroxenic-biotitic porphyrite (Gastaldi’s melaphyre), and the enormous peridotitic masses—occur more especially in the gneiss and mica-schist area of Northern Piémont, that is, in the so-called dioritic belt or ‘Ivrea zone’ which extends from the eastern spurs of the valleys converging near Avigliana, west of Turin, to the Lanzo spurs, and thence north-east to Ivrea, Biella, and the Sesia valley, and beyond the latter to the Strona valley near Lake Orta. The same ‘Ivrea zone’ also extends into the Aosta valley and the valleys descending from Monte Rosa. The amphibolic, prasinitic, euphoditic, and serpentinous series with secondary elements, on the other hand, predominate in the cale-schist and mica-schist area from the upper Lanzo valleys south to Monte Viso and the Maritime Alps, and extend into the Permian and Triassic formations of the latter. The considerable euphoditic and diabasic masses of the Grana and Maira valleys south of Monte Viso are all more or less profoundly metamorphosed to epidotic (zoisitic), amphibolic, and prasinitic rocks,* and therefore do not belong to the category of eruptive rocks with. primitive elements.
The constant and intimate association of the pietre verdi not only with each other but with the stratified mica- and cale-schists led Gastaldi, as previously stated, to regard all those rocks, with the only exception of the primary eruptive rocks of the Ivrea belt, indiscriminately as metamorphosed sedimentary.?, The pietre verdi are now generally recognized to be in the main derived from eruptive rocks and some probably from tuffs or muds. At the same time the constant alternations, amounting to interstratification, of the
1 §. Franchi, ‘‘ Aleune metamorfosi di eufotidi e diabasi Alpi Occid.’’: Boll. R. Com. geol., 1895, p. 181 et seq.
2 Hence his well-known dictum: ‘‘In the Piémontese Alps plutonism is. a myth.”’
P.G. H. Boswell—Quantitative Methods in Stratigraphy. 168
pietre verdi with each other ; their stratiform, if not actually stratified, character in relation to the sedimentary rocks, and their frequent wedges and lenticular intercalations in the latter—all these phenomena on a large scale still present an intricate problem to which I shall refer in the descriptive sequel of the present paper.’ The problem . of the age of the pietre verdi in relation to the older rocks is, of course, rendered more difficult by the obliteration in the latter of organic remains through the ceaseless action of metamorphism past and present, or, in the words of Gastaldi: ‘‘ while Nature gives us on this Karth myriads of living species, she with relentless hand destroys all trace of former life elowne
(To be concluded in our next number.)
TV.—Tuer Apprication or PrerrotogicaL AND Quantirative Mrrnops TO SrraTIGRAPHY. By P. G. H. BOSWELL, A.R.C.Sc., D.I.C., F.G.S., Imperial College, London, S.W. (Concluded from March Number, p. 111.)
LTHOUGH detrital mineral work is as yet initsinfancy, sufficient has been accomplished to show that we may look to it with success for indications of changes of drainage direction, evidences of denudation by reversal of the order of respective miner al assemblages from a sequence of rocks,? and generally for information regarding details of paleogeography. Professor A. de Lapparent referred to Professor L. Cayeux’s work as proving the proximity of land, com- posed of primary rocks, to Lille in Landénian times. Dr. H. H. Thomas was able to demonstrate the change in source, and therefore in direction of drainage, of the river-borne heavy minerals in the Bunter sandstones of South Devon,‘ the occurrence of garnets and staurolite being especially significant. Dr. T. O. Bosworth, in some preliminary work upon the detrital minerals of the Carboniferous Sandstone of the Midland Valley of Scotland, was led to the conclusion, partly by the respective presence and absence of garnets, that the beds could be divided into a series of great lenticular masses of sediment introduced from directions varying from north and north- west to north-east, east, and south.° Mr. W. R. Smellie has discussed in rather more detail the origin of the minerals in the Upper Red Barren Measures of the Glasgow Basin, the drainage having been _ from the west or north-west.® As a result of the study of the Tertiary sediments of Hast Anglia, the writer has been able to prove that the 1 Professor Bonney has described an instructive case of conversion of green- stone into schist on a small scale in the Bernina region, Q.J.G.S., 1894, p. 279 et seq.
2 This idea was suggested for contained boulders by Professor Charles Lapworth in connexion with the Carboniferous conglomerates of Halesowen in Worcestershire.
3 Traité de Géologie, 5th ed., vol. iii, p. 1492, 1906.
4 Q.5.G.S., vol. lviii, p. 620 (Sand of Bunter Pebble- bed), 1902; vol. Ixy, p. 229 (New Red Sandstone), 1909. ° Proc. Geol. Assoc., vol. xxiv, p. 57, 1913. § Trans. Geol. Soe. Glasgow, volt XIV, Pala Glel owe:
164 P.G.H. Boswell— Quantitative Methods in Stratigraphy.
source of the Pliocene material was from the area of the Ardennes, etc., on the south-east, but that the minerals of the Kocene beds were derived from an entirely different direction, possibly from the west or south-west. The overlying Lower Glacial deposits were : derived, as their boulders also indicate, from the north, and possibly the north-east and north-west. These are broad generalizations only, but the subject is susceptible to more exact treatment which would lead to a correspondingly closer realization of ancient changes in geography.
Unconformities are usually emphasized by the changes in mineral composition, and these support paleontological and field-evidence. Changes in the distribution of land and water and in the direction of the large rivers are thus revealed. As an outstanding example may be mentioned the contrast between the fine-grained residues, consisting largely of staurolite, kyanite, tourmaline, hornblende, and pyroxene, which are characteristic of the London Clay in Suffolk, and the coarse muscovite, red garnet, andalusite, staurolite, epidote, etc., of the overlying Boxstones at the base of the Crag of Rupelian, Miocene, or Diestian age.
Recent work has possibly had a tendency to lead geologists to expect too much in certain directions from the comparative study of the residues of sediments, and it should therefore be stated at once that it is improbable that mineral constitution will have any cor- relative value over wide areas, certainly not comparable with that of fossils. From the nature of the subject we should expect various portions of basins of deposition to derive their material from different directions and sources. The writer has, however, endeavoured to show recently that mineral constitution, when fossils are rare or lacking (and if present, of wide range), has a distinct stratigraphical value over limited areas, when abundant samples are collected from numerous localities and horizons.t For this purpose the mineral assemblages of all the divisions of each of the geological stages of a district must be known. In connexion with these statements it should be said that the mineral assemblage of the Lower Greensand over most of its outcrop very closely resembles that of the Reading . Beds of South-East Suffolk and Northern Essex, which beds in turn are extremely similar in mineral composition to the Bagshot Beds of the area around Claygate and Oxshott in Surrey. Again, the mineral constitution of the various divisions of the Eocene beds in Kast and West Kent is much more similar throughout than in the corresponding divisions in East Anglia, where there is a greater variety of minerals. The respective Thanet Beds, Woolwich and Reading Beds, etc., in the two areas do not resemble each other in petrology, and no correlation could be attempted on such evidence alone. The composition of the Thanet Beds around Lille, as detailed by L. Cayeux,? is again different from either. ;
Nevertheless, there are broad groupings which hold over a con- siderable area. Although the members of the Eocene Series differ among themselves, and each member may vary in composition over
1 Abstr. Proc. Geol. Soc., No. 973, p. 76, etc., 1915. 2 Ann. Soc. Géol. Nord, vol. xix, p. 264, 1891; also p. 90.
P.G.H. Boswell—Quantitative Methods in Stratigraphy. 165
a wide area, all the Eocene beds in the London Basin appear to conform more or less to a general type characterized by the occurrence of abundant kyanite, staurolite, tourmaline, zircon, and rutile, and less commonly, green hornblende and small colourless garnets. The various beds of the Pliocene Series from Cornwall to East Anglia and Belgium all possess more or less similar mineral assemblages, the chief members of which are red garnet, muscovite, andalusite, staurolite, epidote, etc. The distinction from the Eocene Series is very marked.
As a final example may be quoted the sands forming the lowest part of the Inferior Oolite, the mineral composition of which is very distinctive, and yet maintains practically the same character when the beds are traced from Yorkshire by way of Northampton, the Cotteswolds, Bath, and Yeovil to the Dorset coast.
While correlation of smaller geological divisions over considerable areas is fraught with difficulty, the mineral constitution of the different beds is of great stratigraphical value, as has been stated, over limited areas. It has been shown, for example, that the Thanet Beds, Reading Beds, and London Clay in East Anglia have each a characteristic mineral assemblage by which they may be recognized, provided that we know also the mineral composition of all the other Tertiary beds from the top of the Chalk to the post-Glacial and Recent.! Speaking generally, each mineral assemblage remains constant over an area of nearly 500 square miles, and appears to be independent of the lithological variations of the bed containing it.’ That there is a limit to this constancy is shown by the fact that the Reading Beds, when traced as far to the south-west as Bishop’s Stortford and Hertford, begin to show a variation in mineral character. The change in mineral composition of the Reading Beds with respect to the underlying Thanet Beds may be due in part to difference of mechanical composition, and therefore to difference in conditions of deposition, resulting in concentration of certain minerals and decomposition of others, but whatever may be the cause the variation observed has an important stratigraphical value. The green and brown hornblende, pyroxene, biotite, apatite, etc., of the Thanet Beds disappear, and it is not until we reach the London Clay that some of these minerals reappear. The large and characteristic grains of kyanite, staurolite, and tourmaline present in the Reading Beds have disappeared in the London Clay, but green hornblende becomes
_ abundant, and muscovite and colourless garnets more common. ‘The detrital material is of fine grain, and therefore provides the more contrast with the very coarse stuff found in the Boxstone Bed at the base of the Suffolk Crags.
1 Abstr. Proc. Geol. Soc., No. 973, p. 76, 1915.
2 Very recently (March, 1916), in a lecture before the Geologists’ Association, my friend and colleague, Mr. V. C. Illing, has claimed that the horizons of the unfossiliferous and oil-bearing sediments of the south-western part of Trinidad may be identified and correlated over a limited area by means of their mineral] assemblages. If this contention is supported by the evidence (and from an examination of the residues I believe it is), the hitherto purely academic study of » the petrology of sediments becomes at one bound of great economic importance.
166 P.G.H. Boswell—Quantitative Methods in Stratigraphy.
The composition of the different zones of the Coralline, Red, and Norwich Crags is similar to, but not of so rich a type as, that of the Boxstones. The Chillesford Beds (late Pliocene) are much enriched in muscovite. The Westleton Beds (? early Pleistocene) show, as compared with the Pliocene beds below and the glacial deposits above, rather an impoverished assemblage which may have been derived from the Chalk and Kocene beds with a slight admixture of Crag detritus (garnets, etc.). The purity of the Westleton pebble- beds (mainly flint and quartz) and freedom from foreign boulders is interesting in this connexion. The glacial deposits yield, as no doubt would be expected when the variety and extent of the rocks laid under contribution are considered, a very rich mineral suite, the abundance and variety of which are unparalleled by any other deposit, and only approached by the Pliocene. Abundant garnets, amphiboles, and pyroxenes (sodic varieties included), epidote, micas, apatite, staurolite, kyanite, tourmaline, etc., make the deposits easily recognizable under the microscope or high-power hand-lens ( X 20). It is noteworthy that andalusite is not nearly so abundant as in the Crag or in the glacial deposits of the West of England. The post- glacial gravels, sands, and brickearths, and the river terrace sands, loams, and alluvium, contain similar mineral assemblages to the glacial beds, and are no doubt derived largely from them.
The value and limitations of the application of petrographic methods to stratigraphy are well illustrated by the consideration of a sequence of deposits in one area such as that just mentioned.
First we may consider the limitations (apart from those resulting from attempted wide correlation). The Upper and Lower Glacial beds of East Anglia differ much in field characters, in mechanical composition, and in their included boulders, indicating two different directions of advance for the ice which produced them. It is very difficult, however, to tell the Upper from the Lower beds by the heavy detrital mineral assemblage, notwithstanding the fact that their mechanical analyses conform to two very different types. This may be due to the mineral richness of each. Again, it was hoped that the various zones of the Red Crag, when traced northwards, might show, together with the increasingly boreal fauna, a corre- sponding change in mineral constitution (the basin was closed on the south and opened on the north in late Pliocene times). No such variation has been observed, and it seems probable that the drainage direction and rocks undergoing denudation to produce the Crag sands, etc., remained the same throughout Pliocene times.
On the other hand, the advantages of the method are great. It has now become possible to identify any East Anglian bed (allowing for the limitations just detailed) from its detrital mineral suite, and to say when the mineral assemblage of any particular bed is pure, or when it has been contaminated with an admixture of material from another bed. A few actual examples may be quoted. Considerable glacial disturbance of the East Anglian deposits has frequently taken place locally in Southern Suffolk, etc., and it is often desirable to _ know whether a limited exposure shows a bed in situ, undisturbed and uncontaminated. Should the bed have been redeposited in
P.G.H. Boswell—Quantitative Methods vn Stratigraphy. 167
Glacial times, even if its original characters are retained, its detrital minerals tell their tale. ‘The pale sands of the Reading Beds, Crag, and Glacial beds often resemble one another closely, and it has hitherto been difficult or impossible to identify with certainty an included mass of such sands in a large glacial disturbance.1 Hxami- nation of the mineral assemblage allows a determination to be made, for example, as to whether the sand is a pure Reading Sand or one contaminated by an admixture of glacial detritus.
The pebble-bed at the base of the London Clay (on the horizon of the Blackheath Beds of the South of England) has in places in East Anglia been rearranged upon the shores of the Crag sea. This is indicated at times by the iridescent ferruginous coating upon the pebbles and the admixture of teeth and coprolites in the bed, but in some cases, except for the presence of reddish sand, it is difficult to say whether the bed is of Kocene or Crag age (that is, rearranged in Red Crag times). An analysis of the sandy material of the bed is sufficient to settle the point, for the Pliocene minerals are distinctive and easily recognizable, while those of the normal Kocene pebble-bed conform to the suite of the Reading Beds.
In the area where overlap of the Thanet Beds by the Reading Beds takes place (in South-West Suffolk and North-West Essex), the latter assume the lithological characters of the former and rest directly on the Chalk. They contain a ‘bull-head’ flint-bed, and are glauconitic clayey sands. When isolated sections in Drift- covered outliers occur on the north-west of the main outcrop, it is sometimes 2 matter of difficulty, as, for example, at Kedington in the Stour Valley, to refer the bed observed to its proper place in the geological sequence. ‘The detrital minerals of the sands will usually be of service, and in the case quoted it was found that, while the Kedington deposit had the lithological characters, etc., of the Thanet Beds, its mineral composition showed it to be an outlier of Reading Beds, resting on the Chalk, but one which had been rearranged on the shore of the Crag sea. Cases might be multiplied, but the limited utility of the method must be apparent.
At present it is premature to discuss the question of the stability of minerals in geological time. ‘The controversy upon the extent to which andalusite occurs in pre-Pliocene sediments in Western Europe is still fresh in our minds. The allied mineral, kyanite, appears to have a well-marked earlier limit in the English area, but how far the _ presence or absence is due to drainage direction is not certain. The extraordinary abundance of sharply crystalline apatite at a loamy horizon of the Thanet Beds near Ipswich, protected by a cover of Chalky Boulder-clay, is noteworthy as showing how an easily decomposable mineral may be preserved.
The investigation of sediments ‘ hermetically sealed’ shortly after their formation, as, for example, gypsiferous deposits in the Permian and Trias, may by comparison yield interesting information as to the amount of decomposition which takes place in heavy minerals sub- sequently to their deposition.
* The disturbance referred to may be 150 yards long and 40 feet deep.
168 P.G. H. Boswell—Quantitative Methods in Stratigraphy.
Oscillatory and alternating current action has an effect, not only in eliminating the more easily decomposable minerals (e.g. some of the ferromagnesian minerals, apatite, andalusite, etc.), but also in concentrating the heavy detritus by a kind of natural jigging or panning. ‘ Pay-streaks’ may thus be produced. Parts of the pebble- bed under the London Clay in Suffolk exhibit an enrichment in zircon, rutile, ilmenite, and magnetite by this action, especially when there is evidence of current-action and contemporaneous erosion.
The lenticles of grains of titaniferous hematite occurring in the basal Cambrian conglomerates of St. Non’s Bay, near St. David’s,! may have a similar origin. The richness of the Bagshot Beds in the heaviest minerals may be attributed to a like cause.
As opposed to this concentration, we have the elimination of minerals (other than those which are more or less unstable) by conditions of deposit. The work of Thoulet and Retgers has shown that micas are absent from certain wind-formed deposits such as desert and dune sands, but examination of British blown-sand dunes has revealed their presence. Topaz tends to form flakes on account of its good basal cleavage, and may well float away; it has been suggested that andalusite may be lost in this way, by floating off during natural or artificial panning. The scarcity of apatite in many deposits is probably due to its disappearance by solution. It is more abundant in clays and loams than in sandstones where percolation is easy, but it does also occur in the latter. When the sediment has to be cleaned by long boiling with acid, much apatite undoubtedly dissolves, but, as in the case of the Boxstone Bed, some still remains. Professor C. G. Cullis and Professor W. G. Fearnsides have both suggested that the difference in solubility may be due to the presence of either or both chlor- or fluor-apatite, but usually the grains are so small, and the occurrence so uncommon, that micro-chemical proof is difficult.
What may be called the intensive study of an area of sedimentary ‘rocks of various geological ages, surrounding an igneous or meta- morphic complex, is at present very necessary for the advancement of our work on the petrology of sediments. For this purpose we need to know exactly and in detail the mineral composition of neighbouring crystalline rocks, slicing alone not being sufficient. Crushing must be resorted to, and panning and separation with heavy liquids, in order that we may be certain of knowing all the accessory and rarer minerals and their relative abundance.? Following this, the study of the neighbouring sediments of varying geological age, considered stratigraphically, cannot fail to yield valuable data which will serve to indicate the extent to which the differences observed in assemblages of detrital minerals may be caused by direction of drainage, conditions of deposition, stability of minerals in geological time, and contemporaneous or subsequent sealing of minerals in sedimentary rocks.
1 'W. Jones, Proc. Geol. Assoc., vol. xxii, p. 232, 1911. 2 R. H. Rastall & W. H. Wilcockson, Proc. Geol. Soc., p. xxx, 1915.
F. R. C. Reed—On the genus Trinucleus. 169
IVY. Concuusron.
Detrital mineral assemblages are of considerable value for strati- graphical purposes over limited areas, but except for very broad divisions, as e.g. Hocene and Pliocene beds, cannot be used for wide correlations. Unlike fossils, minerals cannot show an evolutionary sequence or gradual variation, and there being comparatively so few species occurring in detrital sediments the number of combinations is very limited. Mineral suites, unlike life assemblages, therefore tend to recur. As in the case of minerals of igneous rocks, the relative abundance of the heavy components in sediments is of great determi- native value. Mere lists of detrital minerals occurring in sediments are therefore not sufficient; we need to know the size, colour, form, degree of alteration (if any), and other characters of each mineral, as well as its relative abundance.
The zonal value of mechanical and mineral analyses has not yet been determined, partly because the rocks which yield the best heavy mineral crops, such as sandstones, loams, ete., do not lend themselves to zoning by fossils, while the clays and limestones, which often contain valuable life assemblages, contain frequently only a very small quantity of heavy minerals (other than authigenic). The connexion between the mechanical composition (e.g. of clays), as indicating differences in condition of deposit, and the contained faunas of various zones, has yet to be worked out, but the results may well be interesting.
The goal to be sinned at is a Ienewiedies of the mineral and mechanical composition of every sedimentary rock in the British geological column, collection of material being made over as wide an area as possible. Cores of borings, as well as the records only, must be carefully preserved, and the beds met with subjected to similar analyses. The information obtained should be correlated with that yielded by the distribution of isopachytes and sub-surface ‘contours.
V.—Sepewick Musrum Norss. NorEs on tHE GENUS ZrInucLEUS. Part IV. By F. R. COWPER REED, M.A., Sc.D., F.G.S. (Concluded from the March Number, p. 123.)
MorpHoLocicaL CoRRELATIONS.
EK have now finished the survey of the characters of the head- shield of Trinucleus sufficiently to enable us to discuss the vexed questions of the affinities, systematic position, and evolution of the genus; and from the foregoing details of the various species we can perceive that there are many difficult problems presented when we attempt to correlate its structure with that of other trilobites. Whether the peculiar characters of the genus are the result of degeneration or of the persistent retention of early phylogenetic stages or of a reversion to such stages is a matter of dispute.
170 F, R. C. Reed—On the genus Trinucleus.
Lake,! in regarding the genus Orometopus as the earliest genus of the Trinucleide, concluded that it was not improbable that the ocelli in Zrinucleus represented normal compound eyes in a degenerate condition. Swinnerton? is also inclined to regard the absence of normal facial sutures and eyes not as a sign of early phylogenetic position but as secondary modifications of the Opisthoparian type of head-shield. For he does not consider the marginal suture as homologous with the facial sutures of the Opisthoparia and Proparia. These views are diametrically opposed to those put forward by Beecher,’ on which the classification of the trilobites has of late years been based.
It may be pointed out that the present author, in 1898,* drew attention to the importance of adaptive changes in trilobites in connection with the loss of eyes and to the modifications of the head- shield which accompanied this loss, and it was maintained that blindness was not by itself any evidence of primitive phylogenetic position or of reversion to early stages of development. In the case of Zrinucleus blindness was considered to be an adaptation to special environment. Dollo® has treated this subject at considerable length, and has concluded that 7. concentricus lived in the mud under aphotic conditions as a member of the benthos.
1. Facial Sutures and Genal Areas.
The controversy as to the presence or absence of facial sutures crossing the genal areas (apart from the marginal suture round the fringe) has been waged by many paleontologists.© But no satisfactory evidence of the occurrence of such sutures in young or adult has been produced, and McCoy’s’ figures and description of their presence in his genus Zretaspis are not supported by an examination of the specimens which he used. It is needless to recapitulate here the opinions of the various writers on the subject, for in the case of the English species here studied it has been possible for me to test the accuracy of their observations and conclusions. The line of ‘inquiry which they followed was not often comparative, and the principles of development were not understood by the earlier investigators. The researches of Beecher and other American workers have thrown a flood of light on the ontogeny and phylogeny of the trilobites, and from the adoption of the principles which they have established the position of Zrinucleus has been regarded as fairly secure amongst the most primitive group, Hypoparia. But recently, as above remarked, signs of dissatisfaction with this conclusion have been apparent.
If we regard the genus as now possessing degenerate characters which it has acquired by the loss of certain structures, such as facial
1 Lake, Cambrian Trilobites (Paleont. Soc.), 1907, p. 45.
2 Swinnerton, GEOL. MaG., Dec. VI, Vol. II, p. 489, 1915.
° Beecher, Amer. Journ. Sci., ser. Iv, vol. iii, pp. 89-106, 181-207, 1897.
4 Reed, GEOL. MaG., Dec. IV, Vol. V, pp. 489-47, 552-9, 1898.
> Dollo, Bull. Soc. Géol. Belgique, xxiii, p. 417, 1909.
® Woods, article on Trilobita in The Cambridge Natural History, vol. iv, Crustacea, pp. 226, 230-1, 244-5, 1909.
* McCoy, Syn. Brit. Pal. Foss. Woodw. Mus., p. 146.
F. R. C. Reed—On the genus Trinucleus. (il
sutures and compound eyes, we should naturally turn to its earliest representatives for traces of these structures. It is in the first group, comprising Z. Murchison, T. Gibbsi, and 7. Htheridger, that the division of the genal areas by an oblique ridge is found, and this ridge has the course of the true facial suture in members of the Opisthoparia, and may possibly be regarded as marking the line of fusion between the free and fixed cheeks. The less modified stage in which fusion has not taken place would then be found in the genus Ampyz. In neither case are traces of compound eyes present along this line. The similar position of the pseudo-antennary pit in this genus and in Zrinucleus supports this comparison. Some species of Ampyz (e.g. A. nudus) also have oblique nervures originating from the same place in the axial furrows as in Zrinucleus, and running obliquely back across the cheek to the point of section of the posterior margin by the facial suture, which suggests that they are structures similar to the radiating nervures in Z. Murchisoni, and to the posterior or outer part of the ocular ridge beyond the ocellus in the 7. seticornis group.
In the Conocoryphide (Eastman-Zittel, 1913), in which compound eyes and ocelli are absent, but in which narrow free cheeks are found separated off by true oblique facial sutures, there are groups of nervures radiating out from the same place on the axial furrows as in Zrinucleus. This diffuse innervation of the genal areas is a conspicuous feature amongst blind trilobites, and is especially developed in Liocephalus! of the Conocoryphide and in Dionide. The loss of eyes is found to be correlated with the straightening of the facial sutures and reduction in width and size of the free cheeks in higher genera (e.g. some species of J//enus* and Trimerocephalus)® ; or the facial sutures may entirely disappear by coalescence of the free and fixed cheeks, as in Typhloniscus* and some species of Phacops.°
2. Fringe.
A difficulty meets us at this stage when we cease to regard the marginal suture on the edge of the fringe as representing the conjoint facial sutures as in Beecher’s theory, for the question of its correlation has to be faced. In answer to this we may suggest that it is possible that the lower plate of the fringe represents a reflexed anterior segment of the head-shield, and that the marginal suture is the divisional line between this and the first segment of the superior surface. The bending round ventrally of the anterior part of the crustacean head in its phylogenetic development is part of Bernard’s° annelidan theory of the origin of the Crustacea. Bernard held that — while the typical Crustacean head only consisted of five somites some of the trilobites possessed six somites in the cephalic shield. Early
1 Grénwall, Bornholms Paradoxideslag (Danmarks geol. Undersog., ii, No. 13), 1902, p. 102, t. 2, fig. 2.
2 Reed, Q.J.G.S., vol. lii, pp. 414-16, pl. xx, figs. 1-3, 1896.
3 Gurich, Verh. Kais. min. Ges. St. Petersb., ser. 11, Bd. xxxii, p. 359, +. xv, figs. 7a, b, 1896.
4 Reed, GEou. MaGa., Dec. V, Vol. V, p. 433, pl. xiv, figs. 1-3, 1908.
> Gurich, op. cit., p. 362, t. xv, figs. 4a, b.
© Bernard, Q.J.G.S., vol. 1, p. 411, 1894.
172 Ff. kh. C, Reed—On the genus Trinucleus.
trilobites nearer the annelidan stock and with less fixed ordinal characters might have more segments bent round ventrally than higher forms, and the degree of coalescence of these inverted segments might vary. Thus, in the protaspis of Zrvarthrus there are two segments in front of the glabella which does not reach the anterior margin as it does in Sao; and ifthe immediate ancestors of 7rinucleus had such additional anterior somites one of them might have given rise to the ‘‘ lower plate”’, which, with its genal spines, would thus constitute an exceptionally modified and unfused segment. The
condition of the adult head-shield of Zrinucleus would thus have |
retained more primitive features than any other trilobite. We must admit that the ontogeny of 7. concentricus, so far as it is known, does not support this theory, but we must remember that the larval stages of the earliest species of Zrinucleus are unknown, and we have been led from previous considerations to regard Z. concentricus as one of the more specialized forms. In some other trilobites also the somite repre- sented by the free cheeks (the so-called ‘‘ ocular segment” of Walcott) might not be the first one in the composition of the cephalic shield.
The rostral suture of Calymene and other genera on the above theory might be regarded as the abbreviated representative of the same suture as the marginal one in Zrinucleus, and the epistome as corresponding to the lower plate of the fringe.
Walcott,’ by his study of the Mesonacide, has been led to consider it as not improbable that a seventh segment more anterior than the ‘ocular segment” (i.e. the segment comprising the free cheeks and carrying the compound eyes) existed in the primitive cephalon of the Mesonacide, and he sees traces of it in the larval structure of Olenellus Gulbertt and in the cephalon of Olenelloides and Callavia bicensis; so that in tabulating the somites included in the cephalon he gives first the ‘‘ anterior border segment’, secondly the ‘‘ ocular segment”’, and thirdly the first glabellar segment from which the ocular ridge and palpebral lobe are developed.
It may here be mentioned that though the genal spines belong to the ‘‘ocular segment’ in the Opisthoparia, yet in the Proparia they belong to one of the posterior segments and perhaps to the fourth glabellar segment of the Mesonacide, which in some genera (e.g. Olenelloides) is produced at its lateral termination to form the so-called intergenal spines on the posterior border. The genal spines of the Proparia are therefore not homologous structures with those of the Opisthoparia, a point of importance rarely recognized ; and it would therefore not be wholly contrary to expectation to find the genal spines of the genus Zrinucleus belonging to a different somite of the cephalon, and possibly to the first or ‘‘ anterior border” one of Walcott, bent under ventrally.
Whatever value may be attached to the above theoretical con- siderations, it must be admitted that there is a possible interpretation on these lines, though it would upset our whole accepted ideas of the morphological correlation of the parts of the head-shield.
Another suggestion which may be offered to explain the mar reinal suture is that it is connected with the process of ecdysis; for Limulus
1 Walcott, Smithsonian Mise. Coll., vol. liii, No. 6, p. 238, 1910.
! | \ ‘
F. R. C. Reed—On the genus Trinucleus. 173
and Apus are said to moult by splitting along the frontal edge of the . carapace. This would then have to be regarded as a special adaptation, and perhaps of no phylogenetic importance. The facial sutures in trilobites are usually considered to have been of some use in ecdysis, and compensation for their loss in Zrinucleus may have been obtained by this means.
The fringe would according to this hypothesis be merely brought about by the flattening and broadening of the ordinary cephalic border, while the perforations through its substance might be derived from the multiplication of pits similar to those seen in the marginal furrow of Dionide,’ Harpes, and Euloma.* The lower plate of the fringe would represent the doublure or reflexed portion of the border. The complete fusion of the pits of the upper and lower surfaces of the fringe would be secondary.
3. Ocular Ridges and Nervures.
The history and relations of the ‘‘ ocular ridge” or ‘‘eye-line’”’ in Trinucleus now demand attention. It is generally looked upon as a primitive character. Walcott (op. cit.) has shown how it forms part of the third cephalic (i.e. first glabellar) segment in the case of the Mesonacide; and in Cambrian trilobites belonging to the - Opisthoparia as well as to the Harpedide this structure is well . developed, while, as is well known, it persists in some later genera. It is usually accepted without question that the similarly named structure in Zrinucleus is homologous with this ‘‘eye-line”’ of the Olenide, ete., though in the latter its point of origin does not appear to be so constant, for it frequently arises close to the anterior end of the glabella instead of strictly opposite the first glabellar furrow. It also runs out to compound eyes, not to ocelli, and the eyes are situated on the facial sutures. It is remarkable that in the earliest representatives of the genus Zrimucleus (Group 1) the typical ocular ridge does not occur; but it is found in the larval stages of Z. con- centricus, and is well developed in the adult of 7. setecornis of our second group. Till we know the ontogeny of 7. Murchisoni or its allies we cannot come to the conclusion that the irregular radiating bunch of nervures is more primitive than the definite ocular ridge or optic nerve, at any rate in this genus. But the stratigraphical succession of species points this way, if we dismiss the idea of degeneration.
In most of the Conocoryphide® (e.g. C. Sulzert, Schloth., and Erinnys venulosa, Salt.) there is one of the nervures more strongly developed than the rest, and it forms the trunk from which they branch; its position corresponds with that of the eye-line of the Olenide. If we regard the ocelli of Zrinucleus of Group 2 to be the degenerate successors of the compound eyes of other trilobites and believe that the facial sutures have been obliterated by the complete fusion of the free and fixed cheeks, there is no difficulty in accepting the view supported by Lake and Swinnerton (op. cit.) that the ocular
' Reed, GEOL. MaG., Dec. V, Vol. IX, p. 200, Pl. XI, Figs. 3-6, 1912.
* Brégger, Die Silur. Htagen 2 und 3 (1882), p. 98; Reed, GEOL. MaG., Dec. IV, Vol. VII (1900), pp. 251, 255.
® Grénwall, Bornholms Paradoxideslag, pp. 82-104, 1902.
174 F. R. C. Reed—On the genus Trinucleus.
ridges in Zrinucleus are homologous with those in other genera, such as members of the Olenide. But if we maintain that the marginal suture represents the facial sutures, great difficulties seem to be introduced. For the relics or rudiments of the compound eyes, according to Beecher’s theory, would then have to be sought at the edge or below the edge of the fringe, and the ocular ridges as they now exist must have been shortened considerably. The ocelli then would not be placed at the original terminations of these ‘‘ eye-lines”’ but somewhere along their course, and could not be homologous in position or origin with the compound eyes. The larval characters of T. concentricus, which has the ocular ridge and tubercle developed, do not lend any support to the view that the ocular ridges have been reduced in length and are shrunken remnants of longer ridges. Thus we see another line of evidence tending to contradict Beecher’s theory.
4, Eyes.
The absence of eyes in genera of the higher families is found to be accompanied by modifications in the head-shield on the same lines (apart from the development of a fringe), and no genetic deductions can be drawn from this want of visual organs. In the Illenide, Phacopide, and Cheiruride we find instances of their absence.
On the other hand, the presence of compound eyes is not invariably associated with the retention of facial sutures, as we find in the case of certain species of Acidaspis, in which the sutures have been obliterated or lost by the coalescence of the free and fixed cheeks.
The extension of the ocular ridge to the postero-lateral angle of the genal area may find its explanation in the continuation of the same structure on the ‘‘ocular segment’? in larval forms and some adults of the Mesonacide, and if this is a correct view it would mark the original course of the posterior branch of the facialsuture. There is, however, another explanation possible by which we could regard it as merely the,result of the concentration of those nervures which we found in some of the early species of Zrinucleus convergently trending to this angle. The enlargement of one nerve at the expense of the others in this outer portion of the genal area may have taken place contemporaneously with the development of the ocular ridge from the axial furrow to the ocellus. And in support of this view we find traces of a similar strong nervure in Ampyx nudus, which has a facial suture placed much further out and independent of it.
It may be here mentioned that no lenses have yet been detected in
the so-called ocelli of any species of Zirinucleus, though they are well
developed in Harpes and are schizochroal. The visual function of these genal tubercles in Zrinucleus is generally assumed, but it may be that they had some other sensory function, or that their visual powers (if they are regarded as degenerate compound eyes) have become obsolete. The tubercle on the pseudo-frontal lobe of the glabella, which is generally present in Zrinucleus, and has precisely the same appearance as those on the cheeks, may be representative of the ‘dorsal organ”’ of the Phyllopods, which is supposed to be excretory rather than sensory in its function. But it may represent a median unpaired ocellus, and it is frequently present in species which have
si
Ee
F. R. C. Reed—On the genus Trinucleus. ATS
no genal tubercles, though in some cases it appears to be completely absent. 5. Specialization.
It is not only in the head-shield of Zrinucleus that we can observe extraordinary specialization and the modification or loss of phylo- genetically primitive characters. For the small and constant number of the thoracic segments, and the uniform type of pygidium as well as its relatively large size and its composition of many fused segments, indicate a considerable divergence from and advance beyond the condition of the many-ringed thorax and small pygidium of the Conocoryphide and Olenide or even the Harpedide, in spite of the latter having often been regarded as closely allied to Zrinucleus.
It does not seem that Zrinucleus is in the direct line of any of the other groups of trilobites, but was an early offshoot of the Opistho- paria, to which it is linked (though not by direct phylogenetic connection) by Orometopus and especially Ampyx. Its nearest homcomorphs are Dionide and Harpes, but the latter retains more of the primitive trilobite characters (e.g. many segments to the thorax and a small pygidium), and does not show such extreme specialization except in the head-shield.
Instead, therefore, of placing Zrinucleus as one of the simple lowly types of trilobites illustrating an early stage in the history of the class, it seems more probable that we should regard it as a modified and degenerate form belonging to the Opisthoparia which has been specialized and adapted to a peculiar environment.
Summing up the results of our study of the head-shield of Zrinucleus and balancing the probabilities of the various theories in connection with its structure and origin, we seem led to conclude that the ancestors of this genus branched off from an Opisthoparian stock and suffered degeneration of certain parts in combination with extreme specialization of other parts to fit them for a peculiar environment. Under the aphotic condition of the benthos burrowing in the mud rendered compound eyes unnecessary and they therefore degenerated, while in compensation for the loss of these organs a complete system of nervures developed over the glabella and cheeks. The fixed and free cheeks fused along the line of the facial sutures and ultimately became completely obliterated. The border of the head- shield broadened out and was folded in ventrally so as toform a lower plate, while to facilitate moulting a line of fission was formed along its edge. Perforation of both layers of this border took place on an extensive scale, and the corresponding pits of the two layers frequently communicated. A change of habits in some of the species led to the development of ocelli by rudiments of the compound eyes persisting from larval to adult life, but in other cases this renewal of visual organs was found of no value, and therefore again lost. In conjunction with the presence of the ocelli the optic nerve (ocular ridge) was strengthened and redefined. These changes, which suggest the retention till maturity of larval features or the re-acquisition of organs of which the rudiments had only been left, do not appear to have been strictly successional, but to have been _ developed as occasion required.
176 Reviews—Prof. Joly’s Radio-activity and Geology.
P.S.—Since the above was written Professor Swinnerton’s concluding paper on the classification of the Trilobites has been issued(Gnot. Mae., Dec. VI, Vol. II, p. 543, December, 1915). In it the three families Trinucleide, Raphiophoride, and Harpedide are placed in a separate ' sub-order with three other families as a provisional appendix, and their line of descent is traced back to a Conocoryphid-lke stock. This view is in general accordance with my conclusion that Zrimucleus is more probably connected with the Opisthoparia than with the ill-established group Hypoparia.
RAVLEWwSs-
———<————
I.— Rapio-acrivity AND GEOLOGY.
Tar Braru-time oF THE Wor LD, AND oTHER ScrenTiFic Hssays. By J. Jory, M.A., Sc.D., F.R.S. pp. 307. T. Fisher Unwin. 1915. 10s. 6d. net.
({VHIS volume is an eloquent witness to the love which its versatile author feels for all the activities of nature. It contains twelve essays, mostly written during the last few years, dealing not only with geological problems but also with such diverse subjects as the abundance of life, the colours of flowers, the ‘canals’ of Mars, the photographic image, the application of radium to medicine, and the physics of skating. These last are mentioned only to show the far-flung interests of Professor Joly and the broad appeal of his book; for it will be convenient to restrict the discussion in this place to those of the essays which are specifically geological: The Birth-time of the World, Denudation, Mountain Genesis, Alpine Structure, and Pleochroic Haloes. The problems considered fall approximately into two categories. First, the measurement of eeological time by denudational and radio-active processes, and second, the genesis of mountains. Pleochroic haloes, their explanation, and their application to determining the age of the minerals in which they occur, form the subject of a delightful essay which is already so well known that it calls for no comment here, but one of admiration. Some of the results obtained by Professor Joly for the age of the earth, based on geological methods, are as follows :—
1. From the thickness of sediments . : 100-134 million years. oe a5 mass of sediments : : 87 i 75 3. ua sodium in the ocean . : 99-105 ‘is +4
It is unfortunate that the data used in arriving at an estimate of the detritus borne by the rivers to the sea do not include the recent results for the whole of the United States (Dole & Stabler, Water Sup. Pap., U.S.G.S., No. 284, 1910). Inthe light of this work the figure given for the annual increment of sediment—10,700 million tonnes, + 11 per cent for bottom load—seems to be much too high. Here it may be mentioned that Professor Joly uses the term ‘‘ sedimentary rock’? where mechanically transported detritus is meant, as, for example, when he states that ‘‘ 100 tons of igneous rock yields rather
Reviews—Prof. Joly’s Radio-activity and Geology. 177
less than 70 tons of sedimentary rock” (p. 48). Actually, of course, more than 100 tons of sedimentary rock are produced, because most of the materials carried in solution to the ocean are afterwards incorporated by sediments, and, moreover, a good deal of material is abstracted from the atmosphere during the process of weathering. However, since the same meaning is consistently assigned to ‘‘sedimentary rocks” throughout the calculations, no error is thus introduced in the time estimates.
The amount of sodium annually contributed to the ocean is given as 175 million tons. This figure implies that the sediments now undergoing solvent denudation must lose all the sodium they contain, for the average amount of sodium in sediments, as exposed on the lands, is only 0°85 per cent. Unless, indeed, the igneous and other crystalline rocks of the earth’s surface—and these do not cover more than a quarter of the land areas—also lose all their sodium (and we know they do not), then the sediments must lose more than they appear to have originally contained. ‘This remarkable discrepancy shows either that the statistics of denudation are wrong, or that solvent denudation is now far more active than it has been on an average in the past, or that sodium is in some way restored to the sediments from sea-water. The latter possibility, exemplified by wind-borne salt, is further suggested as probable by the presence of salt waters in deep mines, and by phenomena of adsorption, whereby oceanic salts would become concentrated and trapped in sediments while they yet lay on the sea-floor. That denudation may be unusually active at the present time is a view that Professor Joly does not support. In favour of his contention to the contrary, he quotes figures to show that Europe, with the lowest average elevation among the continents, is undergoing the most rapid denudation. However, it is just in Europe that agricultural pursuits have been longest followed, and who can doubt that agricultural processes may enormously add to the ease with which the natural agents of denudation can attack the land. In ‘the case of the other continents there does appear to be a relation between mean elevation and total denudation. In so far, therefore, as the continents and mountain ranges stand higher to-day than they have averaged in the past, we may expect the intensity of denudation to be correspondingly increased. The remaining possibility, that the statistics of denudation are wrong, only enhances the difficulty, for when the United States data are _ added to those already available, the amount of detritus is found to be less than Joly gives, while the amount of sodium remains practically the same. It is possible, however, that owing to the difficulty of estimating sodium in river waters, errors may arise from inaccuracies of analysis.
If the geological methods of measuring time as interpreted by Professor Joly are reliable, then it is necessary to show in what way the radio-active estimates are wrong. The latter give for the earliest known igneous rocks an age of about 1,500 million years. The pleochroic halo method gives a most probable value of 400 million years for the Leinster Granite (late Silurian or early Devonian).
DECADE VI.—VOL. III.—NO. Iy. 12
178 Reviews—Field Analysis of Minerals.
Professor Joly throws out the suggestion that the rate of transformation of uranium may have been in the past more rapid than now. This, of course, if it could in any way be demonstrated, would necessitate a reduction of the time estimates based on such transformation. The suggestion can, however, be tested in another way, for if the rate of transformation were formerly more rapid than now, then the amount of energy liberated during any given period of the past would also be creater than now. That is to say, if the earth has cooled from a high temperature such as 1,000° C. at or near the surface, the radiothermal energy must have retarded the rate of cooling in the past more tham it does now. Under these circumstances, if the earth were able to cool at all, it would certainly cool so slowly that its age would be much higher than the 1,500 million years required by the accumulation of lead. Joly’s suggestion, then, is incompatible with belief in an earth originally molten at or near the surface. Since no basement. has ever yet been found at the bottom of the geological succession that has not been molten at some time or other, the period required for cooling down to present conditions must have been even greater than that demanded by uninterrupted cooling from a molten state. Thus, the assumption that radio-active transformations have not been uniform leads to far more serious difficulties than does the alternative view that geological processes have not been uniform.
In his essays on mountain genesis and structure, Professor Joly introduces a less controversial subject. He shows that the accumulation of sediments leads not only to thermal blanketing of the rocks beneath, but also to an additional rise of temperature due to the emission of heat from the radio-elements contained in those sediments. In this way, thick lens of sediments and the rocks below them become so weakened by the rising temperature that when the earth contracts they are folded and upheaved by compression, in preference to cooler and more rigid portions of the crust. The process is worked out im convincing detail, and there canbe no doubt that Professor Joly has added to the theory of mountain-building a most significant contribution.
Before closing this review, which by no means covers the whole scope of the book, the writer feels that he should express the pleasure that he has experienced in reading so admirable a collection of essays. The rhythm of life, the majesty of the mountains, the inner secrets of the rocks, and the stimulating companionship of nature—all are revealed in its pages, and reflected in the beautiful photographs with
which they are illustrated. Anceue Eee
IJ.—Fierp Awnatysis or Minerats. By G. D. McGricor. The Mining Magazine, pp. 86. 1915. 3s. 6d. net.
fV\HIS book has been written professedly to meet the requirements
of the traveller.and prospector, and in keeping with that purpose it has been published in a size convenient for the pocket. The advantages of a small strongly bound book in the field may readily be granted, but when the author, in his ‘‘ Prefatory Remarks and Advice’’, recommends the traveller also to take with him Brush
Reviews—Determinative Mineralogy. 179
and Penfield’s bulky Manual and Rutley’s Elements of Mineralogy, one wonders why the smaller book should have been compiled at all. Certainly it only claims to deal with analysis, but analysis alone is generally a cumbersome and sometimes an insufficient means of determining minerals. Asa supplement to the many excellent books on determinative mineralogy which already deal with blowpipe analysis (such, for example, as those noticed below) this little handbook can claim at best only a very limited field. Unnecessary space is devoted to wet methods of analysis, and this might have been better occupied by lists of minerals with their composition and simpler properties. Microcosmic salt is said to be commonly termed ‘micro’; sodium carbonate is referred to as ‘soda’; the use of the scale of hardness is mentioned, though the scale itself is not given.
IJ1.—Dererminative Mrneratocy. ByJ.V. Lewis. Wiley & Sons. 2nd ed., revised. pp. 155. 1915. Price 6s. 6d. net.
‘P\HIS edition differs from the first in no essential particulars, but. it is improved by the addition of several new features that greatly enhance its usefulness. A number of delicate tests have been introduced for various elements or minerals, and the determinative tables have been made more complete. The only blemish that disfigures the pages of the book consists in the use of a large number of abbreviations, many of which are not only ugly but, if saving of space was the ideal sought after, quite unnecessary. The index is good, and the references to any mineral can be located with ease.
IV.—Etements or Mineratoey. By Franx Rouriey; revised by H. H. Reap ; introduction by G. T. Hottoway. Murby & Co. 19thed. pp. 394. 1916. Price 3s. 6d. net.
UTLEY’S well-known book has long been a favourite; among students for its cheapness, among teachers for its thoroughness ‘and general accuracy, and among prospectors for its completeness and convenient size. If this was true of the old ‘ Rutley’, then the present revised and largely rewritten edition ought to enjoy a still higher degree of popularity. Not only is the work brought com- pletely up to date, but the presentation of the facts and the aspect of each printed page is much more attractive than formerly. The inclusion of a chapter on optical properties and its application to the determination of the silicate minerals will be much appreciated. The economic side of mineralogy is given considerable prominence, and attention is directed to the mode of occurrence and uses of minerals rather than to localities alone. The arrangement of minerals according to their most noteworthy element has many advantages, especially from the point of view of determination and economics. In each case an introduction to the element in question is provided, including a list of the chief minerals into which it enters. The book concludes with a useful glossary, a table of the geological systems, and a very complete index. MReviser and publisher are alike to be congratulated on their success in building on the sound foundation of Rutley a most valuable and comprehensive work.
180 Reviews—The E'pigene Profiles of the Desert.
V.—Tue Epiczne Prorites or tar Desert. By A. C. Lawson. University of California Publications, Bull. Dept. Geol., vol. ix, No. 3, pp. 28-48, 1915.
(| \HE author discusses the effects of arid erosion on an uplifted land
mass, and explains the origin of the three elements that enter into the profile thus evolved—rock slopes having an angle of less than 35°, alluvial fans with slopes rarely exceeding 5°, and wide- spread plains. The area to which the paper chiefly refers is that of the Great Basin, in which wind scour is held to be ‘‘an extremely inefficient agent in the evolution of the . . . relief’’. The encroach- ment of alluvial embankments on the rocky slopes is attributed to mechanical disintegration, while scanty rains and occasional cloud- bursts sweep the detritus to lower levels. Ultimately the cycle ‘culminates in the ‘panfan’—a vast alluvial surface of aggradation below which all rock slopes have at last been buried. As corrasion and deflation are dismissed as unimportant, the paper must be regarded as applying to a particular desert rather than to deserts in general.
VI.—Brisr Noriczs.
1. Trrasstc Rocks or Wirrat.—Messrs. Greenwood & Travis have given us part ii of their paper on the Mineralogical and Chemical Constitution of the Triassic Rocks of Wirral. The paper appears, like part i, in the Proc. Liverpool Geol. Soc. (xii (2), 161-88, 1915), and deals with the chemical side. The authors arrive at the general conclusions (1) that the material of the Wirral Trias, as a whole, was derived from igneous rocks of a granitoid nature; (2) that the Bunter and Keuper differ in the physical conditions of the grains, but agree in containing the same minerals; (3) that the Keuper was probably derived direct from the disintegration products of an igneous mass; and (4) that the Bunter had ‘previously formed part “of an earlier arenaceous rock-mass.
2. A New Mernop in Zoockocrarpay.—The study of geographical distribution is so intimately bound up with paleeogeography, and there- fore with geology, that we make no apology for directing the attention of our readers to an important paper by Mr. R. J. Tillyard, M.A., of Hornsby, N.S.W., ‘‘On the Study of Zoogeographical Regions by means of Specific Contours’’ (Proc. Linn. Soc. N.S. Wales, vol. xxxix,
pp. 21-48, pl. i, 1914). Taking a well-defined group, Mr. Tillyard -
plots down the number of species recorded from all known localities, and calls the lines bounding tracts with the same number ‘‘ specific contours’’. He illustrates his method by applying it to the dragon- flies of Australia, with interesting results. Another paper by Mr. Tillyard is a ‘‘ Study of the Odonata of Tasmania in relation to the Bassian Isthmus’’, that portion of land which once (but when ?) connected Tasmania with the Australian mainland (op. cit., vol. xxxvill, pp. 765-78).
3. Tae Form anv Consritution or tHe Earta.—An interesting paper by L. B. Stewart delivered as the Presidential Address to the
i i ln ll a nee
Brief Notices. 181
Royal Astronomical Society of Canada in 1914 (reprinted Smithsonian Rep. for 1914 (1915), pp. 161-74) summarizes recent geodetic work on the form and constitution of the earth. The paper consists mainly of an account of the gradual measurement of the size of the earth, and finally discusses isostasy and allied problems. He accepts isostasy, and adopts the view that the earth is a cooling and shrinking body of which the crust accordingly is under the continual necessity of adapting itself to smaller space; and to this contraction he attributes earthquakes, and as probably none of them originate at a greater depth, he concludes the material at greater depths behaves as a fluid. He also holds the view that the earth as a whole is more rigid than steel. He summarizes the conclusions as to the rate of earthquake waves at different depths.
4. Swattow-warer Depostrion 1n THE CAMBRIAN OF THE CANADIAN CorpituEra.—Under this title Mr. L. D. Burling publishes in the Ottowa Naturalist for November, 1915, evidence of shallow-water conditions during the deposition of Cambrian limestones in British Columbia and Alberta. Such evidences are mud-cracks, ripple-marks, and interformational conglomerate. Such proofs occur in the Middle Cambrian Mount Stephen formation, though not, of course, in the Burgess Shales; also at the base of the Upper Cambrian, in the Bosworth formation, where also are large casts of salt crystals.
5. Tue Favunistic Inrivence oF LitrwoLocicaL CHARACTER.— Mr. L. D. Burling (Bull. Geol. Soc. America, vol. xxv, p. 421) has
studied the relation of the genera and species of Brachiopoda to the
sediments in which they are found, so far as concerns the Cambrian
_.and Lower Ordovician rocks mainly in North America. Dividing
sediments into shale, sandstone, and limestone, he finds that 41 per cent of the genera and sub-genera, 74 per cent of the species and varieties, appear to have been identified from but one type of sediment. About
half of these, however, are represented by single species in single
faunules or localities. Although the nature of the sea-floor does thus appear to exert some influence on the nature and number of the species (there are fewest in shale, most in limestone), still most species can accommodate themselves to changes in the character of the sediment, especially when the change is from more to less elastic. The study is of enough importance to be extended to other groups of animals.
6. Grozocists’ Association or Lonpon.—Mr. George W. Young ended his presidency of this body on February 4, when he read his second annual address ‘‘On the Geological History of Flying”’. This year he dealt with Invertebrates, last year with Vertebrates. Mr. George Barrowe (late of H.M. Geological Survey) succeeded to the presidential chair. The usual list of proposed excursions is issued, many close to London and of exceptional interest. The ‘long excursions’ have not yet been, fixed.
7. Tue Zootoercat Recorp.—The annual volume for 1914 (vol. 11) has just appeared. Paleontologists may be reminded that all fossil forms are included, and that the literature of each group is published separately at a small cost. At the present moment the Zoological
182 Reports & Proceedings—Geological Society of London.
Record is the only list available for 1914. That for 1915 is in preparation, and a list of the parts can be obtained from the Secretary of the Zoological Society.
8.—Opsrp1aN FRomM Hrarnrinnugryeeur, Icetanp: rs Lirnopaysz anp Surface Marxines. By F. E. Wricur. Bull. Geol. Soc. -Am., vol. xxvi, pp. 255-86, 1915.
N his work on the Obsidian Cliff spherulites, Iddings came to the conclusion that the expansion of liberated gases played little part in the development of lithophyse. The examples studied by Dr. Wright indicate, on the contrary, that the volatile components liberated with the radial crystallization of the spherulites ‘‘ aided materially in the original formation and subsequent enlargement of the lithophysal cavities’. Other structures are also discussed, notably surface pits and grooves etched by hot circulating solutions, which bear a striking resemblance to the surface markings of moldavites. While the terrestrial origin of the latter is not proved, it is shown that their external form and internal strains afford no evidence of an extra-terrestrial origin.
REPORTS AND PROCHHDINGS-
I.—Grotoeicat Socrrty oF Lonpon.
ANNUAL GENERAL MEETING.
February 18, 1916.—Dr. A. Smith Woodward, F.R.S., President, in the Chair.
The Reports of the Council and the Library Committee, proofs of which had been previously distributed to the Fellows, were read. It was stated that of the 31 Fellows elected in 1915 (6 less than in 1914), 23 paid their Admission Fees before the end of that year, making, with 8 previously elected Fellows, a total accession of 31 in the course of 1915. During the same period, the losses by death, resignation, and removal amounted to 90 (34 more than in 1914), the actual decrease in the number of Fellows being, therefore 59 (as compared with a decrease of 11 in 1914). The total number of Fellows on December 31, 1915, was 1,250.
The Balance-sheet for that year showed receipts to the amount of £2,836 2s. 10d. (excluding the balance of £105 18s. 5d. brought forward from 1914), and an expenditure of £2,306 7s. 11d.
Reference was made to the fact that three out of the four members of the staff of permanent officers were still engaged in various duties under the War Office, and that temporary assistants had consequently been appointed.
‘The decease of the former Assistant Librarian, Mr. William Rupert | Jones,! was announced, and the awards of the various Medals and Proceeds of Donation Funds? in the gifts of the Council were enumerated.
1 See Obituary, GroL. MaG., February, 1916, p. 96. 2 See brief report, GEOL. MaG., March, 1916, p. 135.
Reports & Proceedings—Geological Society of London. 183
The Report having been received, the President handed the Wollaston Medal, awarded to Dr. Alexander Petrovich Karpinsky, to M. Constantin Nabokoff, Councillor of the Imperial Russian Embassy, addressing him as follows :—
Councillor NABOKOFF,—The Council of the Geological, Society has this year awarded the Wollaston Medal, its highest distinction, to Dr. Alexander P. Karpinsky, Honorary Director of the Geological Committee of Petrograd, which is responsible for the geological survey of the Russian Empire. Dr. Karpinsky’s activities have extended over a period of more than forty years, and so long ago as 1874 he made one of his most important discoveries, that of a marine formation in the Ural Mountains intermediate between the Carboniferous and the Permian Systems. This Artinskian Stage, as Dr. Karpinsky termed it, has now been traced in Russia almost from the Arctic Ocean to the Caspian Sea, besides being recognized in more remote regions, as in the Salt Range of India. Its interesting fauna has also been the subject of several important monographs, of which one of the most valuable is that on the Ammonoids, contributed by Dr. Karpinsky himself to the Imperial Academy of Sciences of Petrograd in 1889. Dr. Karpinsky has continued to take the deepest interest in the geological problems presented by the Urals, and has treated them with remarkable versatility from every point of view, whether tectonic, petrographical, or paleontological ; but as official director of the surveys from 1885 to 1903 he also extended his researches to many other districts, and took a prominent part in the preparation of the beautiful geological maps which were issued during his period of active service. The useful Geological Map of Russia in Europe, which he edited in 1893, is especially well known. All Dr.-Karpinsky’s work is characterized by the most painstaking thoroughness, of which I need only cite his two exhaustive memoirs on the Carboniferous ichthyolite, Helicoprion, as conspicuous examples. Those who have the privilege of his personal acquaintance recognize in him an unassuming and enthusiastic student, still absorbed in following and aiding the progress of our science, and pre-eminently one whom the Geological Society delights to honour. }
The Council will be glad if you will convey this medal to Dr. Karpinsky as a token of its esteem and admiration, with an expression of its best wishes.
Councillor Nabokoff replied in the following words :—
Please accept my sincere thanks for the honour that you have done me in asking - me to come here to-day and to convey to Dr. Karpinsky, with the expression of your good wishes, the Wollaston Medal which the Council of the Geological Society has awarded to him. I feel certain that this great distinction will be deeply appreciated by the recipient of the medal, as well as by the Russian Geological Committee as a high tribute to their Director. My distinguished friend, Dr. H. H. Hayden, Director of the Geological Survey of India, who crossed the Pamirs from India into Russian Turkestan a few months before the War, has often expressed to me the wish and hope that the highly interesting and valuable scientific researches which have been carried out on both sides of the Pamirs by the British and Russian geologists may be linked up and conducted on a basis of firmer and more complete unity and co-ordination. I venture to avail myself of this opportunity of expressing on behalf of my countrymen the same wish, and the confident hope that the ties of friendship which now unite Britain and Russia may extend from the fields of battle to the lofty peaks of science and enlightenment.
The President then handed the Murchison Medal, awarded to Dr. Robert Kidston, F.R.S., to Dr. Finlay Lorimer Kitchin, M.A., for transmission to the recipient, and addressed him as follows :—
Dr. KITcHIN,—The Council has awarded to Dr. Robert Kidston the Murchison Medal as a mark of its appreciation of his numerous and valuable contributions
to our knowledge of fossil plants, especially those of the Carboniferous Period. For nearly forty years he has devoted himself to an exhaustive and successful
184 Reports & Proceedings—Geological Society of London.
study of the external characters of the plant-remains associated with the various coal-seams ; and in this manner he has acquired an unrivalled knowledge of the distribution of the Carboniferous flora, which has proved of fundamental importance both to the geologist and to the practical miner. I may mention, as examples of this work, his classic memoirs on the fossil plants of the Yorkshire and Staffordshire Coalfields and of Belgian Hainaut. During more recent years he has also extended his researches to various facts of structure and morphology which have a direct bearing on evolutionary problems. His memoir on the fructification of Newropteris heterophylla was the first description of the seed of a Pteridosperm in direct continuity with the frond ; while his account of the microsporangia of the Pteridosperms first demonstrated the nature of the male organs in plants of this transitional group. His description of the internal structure of Szgillaria, and his remarkable series of memoirs, with the late Professor Gwynne- Vaughan, on the evolution of the Osmundacexz, must also be specially mentioned. While pursuing his researches he has continually recognized the importance of careful field-work, and has thus made a large and valuable collection of specimens, which has always been placed freely at the disposal of his fellow- paleobotanists. In transmitting this medal, please express our hope that he will treasure it not only as a token of our admiration but also of our gratitude.
Dr. Kitchin replied in the following words :—
Mr. President,—It is gratifying to be the transmitter of the Murchison Medal to one who, a Scotsman himself, has laboured so long and so assiduously in elucidating the stratigraphical bearings of the Carboniferous flora. Dr. Kidston, I feel sure, would have received this medal with enhanced pleasure, could he have listened to your graceful and appreciative references to his work. He asks me to express to you his great regret that he is unable to be here in person ; and I may add that he is detained by responsible public duties, which have the first claim upon his time.
Dr. Kidston writes: ‘* Will you please express to the President my sorrow at not being able to be present to thank the Society personally for the honour that they have done me in presenting me with the Murchison Medal, an honour which, it is needless for me to say, I very much value and appreciate.
‘‘The award of this medal brings vividly to my memory that a number of years ago the Society awarded to me the Balance of the Proceeds of the Murchison Geological Fund, and I would like them to know that these proceeds were spent in the purchase of books dealing with Paleozoic Botany. It is only workers situated where not a single book on their special subject of study is obtainable for reference who can fully appreciate the value of the help that
_I received from that award, and I hope that the books will eventually be placed where they will be of help to others.
‘* T have now only to thank the Council of the Geological Society once more for its kind and encouraging recognition of my work.’’
In presenting the Lyell Medal to Dr. Charles William Andrews, F.R.S., the President addressed him as follows :—
Dr. ANDREWS,—The Council has awarded to you the Lyell Medal as an acknowledgment of the value of your numerous researches in Vertebrate Paleontology. Since your appointment to the Geological Department of the British Museum in 1892, you have made excellent use of the opportunities for research afforded by your official duties, and important contributions to our knowledge of fossil reptiles, birds, and mammals. You were soon attracted by the unique Leeds Collection of Oxfordian marine reptiles, and your studies of this collection eventually culminated in the two handsome volumes of the Descriptive Catalogue, published by the Trustees of the British Museum (1910-13), which must always remain a standard work on Ichthyopterygia, Sauropterygia, and Crocodilia. Your papers on the South American Stereornithes, on Rails from islands in the Southern Seas, and on Prophaéthon from the London Clay, are equally valuable contributions to our knowledge of extinct birds.
Reports & Proceedings—Geological Society of London. 185
Your researches on the fossil mammals of Hgypt, many of them discovered by yourself, are still more noteworthy ; and your Descriptive Catalogue of the Tertiary Vertebrata of the Fayim (Egypt), published by the Trustees of the British Museum in 1906, began a new era in the history of mammalian life. Your demonstration of the stages in the evolution of the Proboscidea and of the relationship between the Proboscidea and the Sirenia, your description and interpretation of the strange Hocene genus Arsinoithertwm, and your recognition of the early differentiation of the Hyracoids in Africa are especially fundamental contributions to biological and geological science. I would further add that all your writings are characterized by remarkable thoroughness and insight into the meaning of the facts described.
As your colleague in the British Museum during the whole period of your service, it gives me great pleasure to hand to you this medal, which the Council of the Geological Society could not have more worthily bestowed.
Dr. Andrews replied in the following words :—
Mr. President, —I wish to express my most sincere thanks to the Council of the Geological Society for the honour that it has done me in awarding to me the Lyell Medal, and to you, sir, for the too flattering terms in which you have made the presentation. Iam particularly pleased to have received this medal from the hands of one with whom I haye been associated for so many years. You will remember that, exactly twenty years ago, you yourself received this award from Dr. Henry Woodward, and that at the same time I received a moiety of the Balance of the Proceeds of the Lyell Geological Fund.
If I have been able to accomplish something in Vertebrate Paleontology, it is mainly due to the fortunate environment in which I have found myself. An assistant in the British Museum possesses quite exceptional advantages, having free access to the great libraries and to the ever-increasing collections, and lastly, but by no means least, having many opportunities of making the personal acquaintance of workers interested in his subject. Having enjoyed these privileges, I feel that I have somewhat fallen short of what I ought to haye accomplished; but, although it is just now uncertain what the future may have in store for us, I hope that I may still have opportunities of doing further work such as will justify this award.
The President then handed the Balance of the Proceeds of the Wollaston Donation Fund, awarded to Mr. William Bourke Wright, -B.A., to Mr. George William Lamplugh, F.R.S., for transmission to the recipient, addressing him as follows :—
Mr. LAMPLUGH,—The Balance of the Proceeds of the Wollaston Donation Fund is awarded to Mr. William Bourke Wright, in recognition of his con- tributions to Quaternary Geology. After completing his geological studies under Professor J. Joly at Dublin University, Mr. Wright joined the Ivish branch of the Geological Survey, and came under the influence of yourself when you were engaged in working out the glacial problems of the Dublin district. He took part in the revision of the memoirs and drift-maps of the Dublin, Belfast, and Cork districts, and shared with Mr. H. B. Maufe the discovery of a continuous raised-beach feature older than the Glacial Period. He also observed this pre-Glacial rock-shelf or beach in the West of Scotland, showing that a general subsidence allowed the sea to enter the valleys along the coasts of the British Isles, almost at the present sea-level, before they were occupied by the ice. After some experience both in Scotland and in England, Mr. Wright returned to Ireland, where, as senior Geologist of the Irish Survey, he has. since been successfully engaged on the glacial geology of the Kenmare and Killarney district. Much of his leisure has been devoted to the preparation of an important work on The Quaternary Ice Age, in which he has made good use of his observations not only in the British Isles but also in Scandinavia. Impressed by the value of Mr. Wright’s researches, the Council will be glad if you will transmit this award to him, with its best wishes for the progress of the work which he has so well begun.
186 Reports & Proceedings—Geological Society of London.
In handing the Balance of the Proceeds of the Murchison Geological Fund, awarded to Mr. George Walter Tyrrell, F.G.S., to Dr. Herbert Lapworth, Sec. G.S., for transmission to the recipient, the President addressed him in the following words :—
Dr. LAPWORTH,—The Balance of the Proceeds of the Murchison Fund has been awarded to Mr. G. W. Tyrrell in recognition of his contributions to the petrology of South-Western Scotland. His keen petrographic insight was first shown in his description of the quartz-dolerite sills of Kilsyth. His results of most general interest to geologists are those connected with the Paleozoic alkaline rocks; for his investigation of Lugarite has added to petrology a peculiar rock-species and important evidence in favour of the differentiation of igneous rocks by the sinking of their heavier constituents. In several papers on the Auchineden Hills he has described their igneous rocks and their glacial and physical features; and in his recent account of the ravine known as the Whangie he has advanced conclusive evidence of its formation by earth- movements. As the Senior Assistant in the Geological Department of Glasgow University, and later also as Lecturer on Petrology there, he has done much towards the development of that school of geology. The Council hopes that this award may encourage and assist him in further research.
The President then presented a moiety of the Balance of the Proceeds of the Lyell Geological Fund to Mr. Martin A. C. Hinton,
addressing him as follows :—
Mr. HINTON,—The Council has awarded to you a moiety of the Proceeds of the Lyell Fund in recognition of your researches on the British Pleistocene Mammalia, and as an incentive to further work of the same kind. Under circumstances frequently discouraging, you have for many years devoted yourself especially to the study of the Rodentia and the Insectivora, and have obtained a remarkable knowledge of the skeleton and teeth of certain groups which are most commonly met with among fossils. In this manner you have made discoveries with an important bearing on many problems of Pleistocene geology, which you have never failed to recognize. As one who has followed your work with great interest for several years, it gives me much pleasure to hand you this award.
The President presented the other moiety of the Balance of the Proceeds of the Lyell Geological Fund to Mr. Alfred Santer Kennard, F.G.8., addressing him in the following words :—
Mr. KENNARD,—It is particularly appropriate that the second moiety of the Proceeds of the Lyell Fund should be awarded to you, who have worked so long and so successfully with Mr. Hinton at problems of Pleistocene geology in the South of England. In the leisure of a busy life you also have made yourself thoroughly acquainted with a group of fossils, the Non-marine Mollusca, which are of fundamental importance in classifying and interpreting the various deposits in which they occur. Both alone and with Mr. B. B. Woodward you have published many interesting notes and lists of such Mollusca from Pleistocene and Holocene deposits in different parts of Britam. The Council desires to acknowledge the value of this work, and I have much pleasure in handing to you a tangible expression-of its good wishes.
The President thereafter proceeded to read his Anniversary Address, giving obituary notices of Count Solms-Laubach (elected a Foreign Member in 1906), René Zeiller (el. For. Memb. 1909), Kdmond Rigaux (elected a Foreign Correspondent in 18938), and Michel F. Mourlon (el. For. Corresp. 1899), as also of the following Fellows: James Geikie (el. 1873), H. H. Howell (el. 1853), R. Lydekker (el. 1883, resigned 1915), C. Callaway (el. 1875, resigned 1906), A. Vaughan (el. 1900), O. A. Derby (el. 1884), W. Anderson
Ls
Lg & Proceedings—Geological Society of London. 187
i 1899), H. Kynaston (el. 1894), W. G. Adams (el. 1865), R. Assheton (el. 1886), Hon. Robert Marsham-Townshend (el. 1859), Sir Sandford Fleming (el. 1877), F. W. Millet (el. 1900), A. Dunlop (el. 1874) G. H. Hollingsworth (el. 1879), B. Holgate (el. 1877), W. Simpson (el. 1893), J. T. Hotblack (el. 1900), H. ‘Rote (el. 1890), D. A. Louis (el. 1909), H. S. Bion (el. 1911), W. J. Clunies Ross (el. 1882), and others. He also referred to the death of William Rupert Jones, late Assistant Librarian.
The President then discussed the use of fossil remains of the higher vertebrates in stratigraphical geology. ‘The study of fossil fishes, to which he had referred in his Address of 1915, raised the question as to whether animals of apparently the same family, genus, or species might not originate more than once from separate series of ancestors. The higher vertebrates, which inhabited the land, might most profitably be examined to throw light on the subject; for the land has always been subdivided into well-defined areas, isolated by seas, mountains, and deserts, so that animals in these several areas must often have developed independently for long periods. Students of shells are unanimous in recognizing what they term homcomorphy, and trace immature, mature, and senile stages in the course of every race that can be followed through successive geological formations. Vertebrate skeletons, which have much more numerous and tangible characters, and approach senility in more varied ways, should afford a clearer view of general principles.
Even among vertebrates the evidence that most concerns the geologist is not always easily interpreted. For instance, the Sparassodonta and horned tortoises of the Argentine Tertiary are ‘so closely similar to the existing Thylacines and the fossil Miolania of Australia, that they are still sometimes quoted as proving the former existence of an Antarctic Continent uniting the South American and Australian regions. On the other hand, they may be
‘merely survivors of cosmopolitan races at the two extremes of their
former range, with certain inevitable (but not altogether similar) marks of senility. In making comparisons, indeed, it is no longer enough to distinguish the fundamental and merely adaptive characters of animals; it is also essential to note separately those characters which depend on the early, mature, or senile position of the particular animals in the evolving series to which they belong.
Hitherto there seems to be only one case in which we have enough materials for forming a judgment as to whether a fundamental advance may occur more than once. Mammal-like reptiles are abundant in the Permian of North America and in the Permian and Trias of South Africa and other parts of the Old World. Recent studies have shown that all specializations in the North American forms are in the direction of higher reptiles, while all those in the South African forms are in the direction of mammals. Hence, although there is evidence of two possible sources of mammals, only one appears to have produced them.
Among advances of lower degree, the origin of the monkeys or lower Anthropoidea may be considered. It is agreed that they arose from the Lemuroidea which were almost universally distributed over
188 Reports & Proceedings—Edinburgh Geological Society.
the great continents at the beginning of the Tertiary era. They seem to have evolved separately in America and in the Old World, but the two series are very sharply distinguished, although they form one zoological ‘sub-order’. When isolated on the island of Madagascar, some of the same animals acquired a few peculiarities of the American, others of the Old World Anthropoidea, but never
really advanced beyond the Lemuroid stage, merely becoming senile
just before their extinction. Hence, the Lemuroidea evolved in three different ways, and the resulting groups are very easily distinguished.
The study of the Tertiary Ungulata is especially important, because most of the groups arose either in North America or in the Old World, which were united and separated several times. It seems clear that, although each group probably originated but once in one particular area, its members soon diverged into several independently evolving series, each imbued with some definite impulse or momentum towards specialization in the same way in the course of geological time, only at different rates. There were thus, for example, several distinct lines of horses and rhinoceroses, but all from the same source.
It is now well known that the characteristic South American Tertiary Ungulates arose in an isolated area, and many of their specializations are curiously similar to some of those observed among Kuropean Eocene and Oligocene Ungulata which soon proved abortive or ‘inadaptive’. They are, however, by no means identical.
While so many changes have occurred during the evolution of the vertebrates, the persistence of characters and the strength of heredity in numerous cases are still as Petplexing as they were when Huxley first directed special attention to ‘ persistent types’. The President enumerated some illustrations.
The ballot for the Officers and Council was taken, and the following were declared duly elected for the ensuing year :—
OFFICERS (who are also ex-officio members of the Council) : President: Alfred Harker, M.A., LL.D., F.R.S. Vice-Presidents: Sir Thomas Henry Holland, K.C.I.E., D.Sc., F.R.S.; Edwin Tulley Newton, F.R.S.; the Rey. Henry Hoyte Winwood, M.A. ; and Arthur Smith Woodward, LL. D, F.R.S. Secretaries: Herbert Henry Thomas, M.A., Se.D.; and Herbert Lapworth, D.Se., M.Inst.C.E. Foreign Secretary: Sir Archibald Geikie, O.M., K.C.B., D.C.L., LL.D., Se.D., F.R.S. Treasurer: Bedford McNeill, Assoc. R.S.M.
CouncIL: Henry Bury, M.A., F.L.8. ; Professor John Cadman, C.M.G., D.Se., M.Inst.C.E.; Professor Charles Gilbert Cullis, D.Sce.; R. Mountford Deeley, M.Inst.C.E.; Professor William George Fearnsides, M.A.; Walcot Gibson, D.Se.; Finlay Lorimer Kitchin, M.A., Ph.D.; John Edward Marr, M.A., Se.D., F.R.S.; Richard Dixon Oldham, F.R.S. ; Robert Heron Rastall, M.A.; Professor Thomas Franklin Sibly, D.Sc.; Professor William Johnson Sollas, M:A., Sc.D., LL.D., F.R.S.; J. J. Harris Teall, M.A., D.Se., LL.D., - F.R.S.; William Whitaker, B.A., F.R.S.
II.—Epinsurexw GrotocicaL Socrery. February 16, 1916.—Dr. Robert Campbell, President, in the Chair. ““Some Obscure Factors in Coastal Changes.”? By Professor Thomas J. Jehu, M.A., M.D., F.R.S.E., F.G.S. Factors affecting the development of the coastline were considered under three headings—(1) Changes in the relative level of land and
Correspondence—J. W. Evans. — 189
sea; (2) erosion; and (3) accretion. Since Neolithic man arrived in Britain, there is evidence of a submergence along the coasts of England and Wales and the Sonth of Ireland, and of an emergence along the coasts of Scotland and the North of Ireland. These movements took place prior to the time of the Roman occupation of Britain. Whether movements have taken place in still more recent times is somewhat doubtful, but there are slight indications of a subsidence in the extreme North of Scotland, and at one or two places on the coasts of England and Wales. Reference was made to the need of systematic observations being carried out by the Ordnance Survey to ascertain whether such movements are now in progress, and, if so, to what extent.
Estimates were given as to the extent of erosion and accretion in the United Kingdom within recent years, and it was shown that more land had been gained by accretion and artificial reclamation than has been lost by erosion. But while the gain has been almost entirely in tidal estuaries, the loss has been on the open coasts. Further, the gains have been due not so much to the accumulation of material eroded by the sea as to the deposition of sediment brought down by rivers from their drainage areas.
The serious erosion on the coasts of Holderness and of East Anglia were described and illustrated by views. While the chief agents of erosion are well understood, it was pointed out that there is a great lack of knowledge as to what takes place below the level of low water. Observations are needed regarding such questions as submarine erosion, the travel of material below the low-water line, and the movements of outlying sandbanks. There is much obscurity as to the limits of depth at which materials are moved on the floor of the submerged continental platform by waves of current action, or both combined; and again as to what depth the movement of detritus on the sea-floor is really effective in producing abrasion. The intermittent character of the erosion at many places on the east coast of England was noted as a puzzling fact. It may be due to an alteration in the point of attack of the sea on the coastline, brought about by the shifting of outlying sandbanks or shoals. .
Another factor in erosion, the importance of which has been over- looked, is the action of rock-boring organisms. An account was given of the present state of knowledge regarding their work and of their effect on the sea-bed near Cromer. Little is known as yet as to the rate of boring, or as to the depth to which it occurs.
CORRESPON DHNCE.
DIFFERENTIATION IN IGNEOUS ROCKS.
Sir,—Having occasion to refer to the report of my contribution to the discussion ‘‘Sur la différentiation dans les magmas ignés”’ at the Toronto Geological Congress, in the Compte Rendu (pp. 248-9), I find that through some typographical accident, which in the absence of a proof remained uncorrected, the meaning of one paragraph has been seriously obscured.
190 Obituary—Professor John Wesley Judd.
After suggesting that the presence of a considerable amount of water in a magma might result in its separation in the liquid state into two immiscible portions, the lighter containing the greater part of the water and of the more acid and alkaline constituents, representing quartz and the alkali felspars, and the heavier consisting mainly of the basic constituents with comparatively little water, I continued: ‘‘Tt was to be expected that the character of the differentiation would depend on the amount of water present. If this were larger, one would expect a comparatively complete removal of the alkali felspar materials.’” [‘‘ With less water one may expect a greater amount of the alkaline material to remain with the more basic portion”’], ‘‘ and with further differentiation by other processes this would naturally give rise to a series of rocks of the alkali or ‘Atlantic’ type. This suggestion—it was intended to be nothing more—appeared to derive some support from the frequent association of rocks of this character with block faulting, while rocks of the normal or ‘ Pacific’ type were usually found within areas characterized by folding, where there was less facility for the escape of water to the surface.”
The words in square brackets are those actually used in the first draft of the summary of my remarks supplied to the Secretary of the Congress. ‘hey were probably modified in the fair copy, but those appearing in their place in the printed text do not make sense. Indeed, the only meaning that might be extracted from them would be exactly the opposite of that intended, as shown by the context. A brief but correct version will, however, be found in my contribution to the discussion on a paper by Professor P. Marshall (Quart. Journ. Geol. Soc., vol. xx, p. 406, 1914).
It is immaterial for the present purpose whether my suggestion with regard to the origin and distribution of the alkali rocks was well founded. I merely wish to have it correctly recorded.
J. W. Evans. IMPERIAL COLLEGE OF SCIENCE AND TECHNOLOGY (RoyAL SCHOOL OF MINES). March 9, 1916.
(Spsresay Ops Sg
PROFESSOR JOHN WESLEY JUDD.
Many friends and numerous old pupils will deeply regret the death of Professor J. W. Judd, who passed away at nis home in Kew on March 8. In 1905, when he retired from the Chair of Geology in the Royal College of Science, this Magazine published the story of his life, with.a list of his many contributions to science, so that it will now suffice to continue that story to the closing days. These were spent either at Kew or at a small house which he had acquired at Walmer; for he had ceased to travel, partly on account of his own health, since before retirement he had begun to suffer from a form of
Obitwary—Professor John Wesley Judd. 191
deafness which is often associated with vertigo, and partly because that of one of his two children required constant watchfulness. His own physical trouble, which happily did not materially increase, was just sufficient to cause his gradual disappearance from scientific gatherings in London. Still, he was my guest in Cambridge at the Darwin Celebration in 1909, and it. was not till the outbreak of the present War that any serious failure became marked. Of that War he may be regarded as an indirect victim. Its horrors at the present and its ominous promises for the future were a bitter disappointment to a man of his sympathetic nature. The thought of them depressed his spirit by day and haunted his dreams by night. Rather more than a year ago he began to suffer much from neuritic pains, which often cramped his limbs and impeded his movements. A visit to Walmer during last summer sent him back to Kew in a more hopeful condition, but no long time afterwards he began steadily to lose strength, till at last he literally fell asleep.
I can heartily endorse every word that a writer in this Magazine has already said in Judd’s praise as a geologist and a friend, alike to those of his own standing and to his pupils; for I have known him intimately for some forty years. We were Joint Secretaries to the Geological Society from 1878 to 1884, and he continued his services while I was President. We have met on many committees and as fellow-examiners, and in matters connected with the Funafuti boring, where he did a heavy piece of work in connexion with the examination and transport of the cores. We did not always quite agree on geological questions and matters of policy, but that never affected the constancy of his friendship. More than once he has gone out of his way to do me valuable service, and I have never met with a man who was less of a self-advertiser and self-seeker, or was more considerate of others. He was inflexible in taking the course to which, in his opinion, duty pointed; but his quiet, almost imperturbable, manner was united with a truly warm heart.
Though during the last ten years new investigations had become practically impossible, he still made valuable contributions to geological literature. The most important of these, for it is needless to enumerate every ‘‘ chip from his workshop”, were the following: “Henry Clifton Sorby and the Birth of Microscopic Petrology ” (this Magazine, 1908, p. 193); ‘‘ Darwin and Geology,” an essay in Darwin and Modern Science (1909); The Coming of Evolution, published in the Cambridge Manuals of Science and Literature (1910); Zhe Students’ Lyell, his second, revised and enlarged edition of Lyell’s Students’ Elements of Geology (1911); and an obituary of Sir Joseph Dalton Hooker, contributed to Professor Watts’ Presidential Address to the Geological Society in February, 1912. Judd’s last communication to that Society was on March 25, 1914, when he gave a succinct account of the Island of Rockall as a preface to a paper on its unusual rock by Dr. H. 8S. Washington. All these maintained a high level, and the Coming of Evolution is a most attractive book, both from the writer’s intimacy with Darwin and the ‘ dauntless three”? who stood beside him in that conflict and from its remarkable literary grace.
192 Miscellaneous.
As initiator and organizer of the system of instruction in geology at South Kensington, already so well described in this Magazine, Judd did a great work, for this system was then unequalled in Britain and has never been surpassed. On that point I can speak with confidence, since I acted for some years as his external examiner, and have had, in a similar capacity, considerable experience elsewhere. The results were admirable, and continue to be so under his successor, and it is therefore regrettable that, when Judd retired in 1905, his pension was calculated, on technical grounds, not from the date of his appointment to office in 1876, when he at once devoted ~ his whole time to the work, but from 1881, when that became obligatory. It is, however, still possible to mitigate the injustice, for such it really was, by means of a pension from the Civil List to those who survive him. His only reward was the barren honour of being nominated Emeritus Professor of the Imperial College in 1913.
T. G. Bonner.
MISCHILLAN HOUS.-
—_—_@—___ Tar Crosine or NarronaL GxEoLogicaAL CoLLECTIONS.
Although it is not the habit of this Magazine to intermeddle with politics it seems desirable to put on record Government action with regard to National Geological Collections. A full account of the action of the Government is printed in the Museums Journal for March, including a verbatim report of the speeches in the Lords, the Deputation to the Prime Minister, and the comments of the German and Austrian Press.
The report by the Retrenchment Committee was very severely handled in the Zimes by ‘‘ A Biological F.R.S.”, and among the more noteworthy letters that appeared in that newspaper were those of Sir Ray Lankester, who commented on the ignorance of the political Trustees of the British Museum, and the letter of the Speaker of the House of Commons (himself a principal Trustee of the British Museum), a letter which completely justified Lankester’s biting satire.
The final result is that at the British Museum (Natural History) the galleries of Fossil’ Mammalia and Reptilia and the Gallery of Mineralogy will be open to the public on Monday, Wednesday, and Friday ; the other collections of fossils will be closed continuously. But so long as sufficient staff is available any student can have access to the collections at the normal times by personal application to a member of the staff.
As regards the Museum of Practical Geology, it is ‘‘ closed to the general public’’, but the Geological Survey Offices, with the Map Room and Library, which are approachable only through the Museum, are open as usual. Teachers with their classes are still permitted to have access to maps, photographs, and other illustrations of the Survey’s work.
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THE
GEOLOGICAL MAGAZINE
NEW SERIES. DECADE VI. VOL fiisonian lngzj-s
No. V.—MAY, 1916. {
ORIGIN AL ARTICLES. Laren Ae On al Muse %
I.—Tue PrrrocraPHy oF ARRAN. me eels Us 3. Prreustone XeEnouiTHs in Basatr Dyker, Drepin, ARray.'
By G. W. TYRRELL, A.R.C.Sc., F.G.S., Lecturer in Mineralogy and Petrology, University of Glasgow. ‘{\HE phenomenon of which this paper treats occurs in a basalt | dyke exposed in a small quarry by the roadside north-east of Dippin, near the twelfth milestone from Brodick. This dyke runs from north-west to south-east, and is intrusive into the great teschenite (or crinanite) sill of Dippin. It is probably the one referred to in the Geological Survey Memoir on North Arran, South Bute, and the Cumbraes (1903), p. 119. It averages 12 feet in thickness, although it is extremely irregular, owing perhaps to the difficulty experienced in penetrating the tough, coarse, massive rock of the sill. The contacts are not plane, but abut against the crinanite in a very intricate manner, sometimes along vertical or horizontal joints, sometimes along irregular surfaces unconnected with jointing. Both contacts show thin films of tachylyte, which, as the rock is quarried, are left adhering to the irregular surfaces of the sill rock. Another dyke-like mass, 1 foot thick, is seen in the same quarry, and is doubtless an offshoot from the larger dyke.
Within a foot of the northern contact of the larger dyke there are found enclosed several lumps of brown and black glassy rocks con- taining a few large white crystals of felspar. These lumps range from 1 to 8 inches in diameter, and are each surrounded by a thin film of tachylyte, while small clots of a black glass are to be found in their vicinity. Other xenoliths found near by consist of a medium- grained crystalline rock resembling the crinanite of the Dippin sill. These are larger than the glassy xenoliths and are quite evidently affected by heat. ‘They are also surrounded by a skin and sometimes clots of tachylyte.
The Dyke.—The dyke belongs to a distinctive group of the Tertiary: north-west dykes, which appears to be abundantly distributed about the Clyde Estuary. These dykes have frequently been called ‘basaltic andesite’ or ‘andesitic basalt’, and are distinguished by containing beautifully fresh phenocrysts of anorthite or bytownite, in a ground-mass composed of laths of labradorite, augite frequently intergrown with enstatite or hypersthene, and an abundant mesostasis
1 The first two papers of this series appeared in the Gro. Maa., Dec. V, Vol. X, pp. 305-9, 1913. }
DECADE VI.—VOL. III.—NO. V. 13
4 OCT 211916 %
194 G. W. Tyrrell—The Petrography of Arran.
of dark glass. From their abundance in the island of Great Cumbrae, situated in the Firth of Clyde, it is proposed to distinguish them as the Cumbrae type of basalt. The Tynemouth dyke of the North of England appears to be an outlying member of the same series.
In thin section the rock from the centre of the dyke shows small but rather numerous phenocrysts of plagioclase felspar which are occasionally euhedral, but are more often worn and corroded into curious irregular shapes. Whatever the shape, all the crystals possess a narrow marginal zone of different composition orientated similarly to the main mass. ‘I'he transition between the two parts is usually quite sharp. The measurement of extinction angles shows that the crystals are bytownite (Ab,An,) with marginal labradorite. There are also a few phenocrysts of fresh enstatite, showing a good positive biaxial figure in basal section ; and fewer still of a yellowish augite. The ground-mass is composed of zonal labradorite laths, intermixed with prismoids of augite and grains of iron-ore, with an abundant mesostasis apparently of a felspathic substance, crowded with black hair-like microlites, and probably representing a de- vitrified glass.
This rock is an andesitic basalt or basaltic andesite generally similar to the Tynemouth and Cleveland dykes of the North of England. Other dykes of the same character, with slight variations in texture, amount of glass, or abundance of phenocrysts, occur in the vicinity, cutting the Dippin sill and the adjacent Triassic sandstones.
Traced towards the margin of the dyke the rock becomes denser, and contains fewer and smaller felspar phenocrysts. A specimen taken 3 inches from the margin shows a beautiful variolitic texture in thin section. The felspars of the ground-mass are reduced to the size of large microlites, and are arranged in irregular radiating bundles or sheaves which involve numerous long prisms of augite and grains of iron-ore.
At the actual margin the rock is tachylytic for a thickness of + inch. In thin section the glass is dark, opaque, and almost structureless, with only a few obscure microlites. It contains numerous small spherical amygdales of calcite, and a few small phenocrysts of labradorite with the usual rounded or irregular outlines indicating magmatic corrosion.
The Xenoliths.—The great majority of the xenoliths are of pitch- stone. In thin section the bulk of this rock is seen to consist of a pure, almost colourless glass, in which hair-like microlites are aggregated into clots or patches, leaving -large areas of glass absolutely free from microlites. The phenocrysts are of euhedral quartz, orthoclase, and andesine (Ab;An,). The effects of the heat to which this rock has been subjected are striking. Of the three principal minerals orthoclase has suffered the most, andesine much less, and quartz hardly at all. The orthoclase in all cases shows some degree of fusion, which has occurred around the margins and along the cleavages, producing a yellow or greyish glass which contrasts with the lighter glass of the ground-mass. The resulting shapes of the crystals are highly irregular; occasionally the crystal
ee ee ee eS
G. W. Tyrrell—The Petrography of Arran. 195
is separated into two or three pieces by areas of fusion; but in extreme cases the crystal is represented by a ‘ ghost’ in greyish glass, in which only minute shreds of the original orthoclase have survived.
The andesine crystals have apparently only suffered a little softening on the margins and fissuring in the interiors. The quartz has suffered least of all, as the crystals are only fractured. The fact that the broken pieces have occasionally floated away from one another is evidence that the glass of the pitchstone was rendered completely liquid by the degree of heat to which it was subjected.
Kach xenolith is surrounded by a skin and sometimes clots of a black glass, which was at first regarded as a tachylyte of the same nature as that on the margins of the dyke. A thin section, however, shows that this material is really a colourless glass which is darkened by numberless lines, streaks, and patches of black dots, arranged with a perfect fluxional structure. The glass contains the same set of phenocrysts as the above-described pitchstone, but much smaller and fewer. Under a high-power objective the black dots which darken the glass are made out to be small, perfectly euhedral, hexagonal tablets of hematite, the larger ones translucent and of a blood-red colour.
The difference between this rock and the pitchstone it envelops may be explained thus: the xenoliths have not only been perfectly fused, but the pitchstone glass has intermingled to some extent with the more basic glass of the basalt in which the xenoliths were carried up, the admixture of basalt glass resulting in the formation of swarms of hematite microlites. The flow-structure may have been imparted by a rolling motion of the xenoliths, due to differential velocity of the central and marginal parts of the basalt dyke during intrusion. The xenoliths are found within one foot of the margin, where movement would be retarded by cooling and viscosity on the marginal side, whilst proceeding at a faster rate in the more liquid interior.
Conclusions.—The behaviour of the phenocrysts in the pitchstone xenoliths under the influence of heat gives some clue as to the
.temperature of the basaltic magma in which they were immersed. The orthoclase was partially or wholly fused to a yellow or grey glass, andesine showed signs of softening around the edges, whilst quartz simply suffered some degree of fracturing. The most trust- worthy estimates of the fusion-points of rock-forming minerals have been made by A. L. Day and his collaborators in the Geophysical Laboratory at Washington.’ That of quartz (or rather silica, since quartz is unstable above 800° C.) is given as 1,625° C.; of oligoclase-andesine (Ab, An,) as 1,375° C. For orthoclase, however, we have to rely on the estimates of other experimenters.? The average of seven closely accordant estimates by Joly and Cusack, and Doelter, is 1,170° C. These figures are as would be expected from the effects produced by heat on these minerals. Orthoclase, which fuses at 1,170° C., has been converted into glass; andesine,
1 Clarke, Data of Geochenustry, 2nd Ed., U.S. Geol. Surv., Bull. 491, p. 279, 1911. 2 Iddings, Igneous Rocks, vol. i, p. 85, 1909.
196 Dr. Wyatt Wingrave—A New Variety of Ammonite.
fusing in the neighbourhood of 1,375° C., has barely been affected ; quartz, fusing at 1,625° C., has only suffered fracturing. We may therefore conclude that the temperature of the basaltic magma during intrusion was between 1,170° C. and 1,375° C., excluding, as seems legitimate, any chemical reaction between orthoclase and the pitchstone glass. The ordinary basalt lava is fusible at about 1,100° C., and this is perhaps the ordinary temperature of emission at a volcano, although Daly believes temperatures of 1,200° C., or even 1,300° C., may prevail in the great volcanoes of Hawaii at periods of intense activity." The fusion of minerals and even rocks has been observed in basaltic magmas by Lacroix and others.’ Independent evidence of high temperature upon intrusion in the case of the dyke in question is afforded by its tachylytic selvages. These are due to very rapid marginal cooling, and the rate of cooling depends directly on the difference between the temperature of the country rock and of the magma.
The occurrence of xenoliths of pitchstone in a Cumbrae type of basalt, which itself intrudes a sill of teschenite or crinanite, affords useful evidence as to the relative ages of these three groups of intrusive rocks. A pitchstone dyke with a felsitic centre cuts the Dippin crinanite near Torr an Loisgte, about 13 miles north-west of the quarry in which the xenoliths are found.s This dyke trends in a north-west direction, and would therefore, if produced, appear in the vicinity of the quarry, beneath the crinanite sill. It is possible that fragments of this dyke have been brought up by the basaltic magma. ‘The sequence of the three types in time is clearly, first the crinanite sill, then the pitchstone, and finally the Cumbrae basalt. Similar evidence from other parts of the island goes to show that the Cumbrae basalts were one of the latest manifestations of igneous activity in Arran, if not the latest.
IIl.—A New Variety or THE AmmonitR Ca@ztocrrés DAV 41, FRoM tHE Lower Lis, Dorser.
By WYATT WINGRAVE, M.D. (PLATE VIII.)
UENSTEDT ‘ described three distinct varieties of Ammonites Dave, with nine illustrations. They all belonged to the y zone of Lower Lias :—
1. Ammonites Davai, whose tubercles are somewhat clavate and with unsymmetrical prorsiradiate ribs.
2. A. Davei enodis is continental. It is a small specimen without tubercles, with fine symmetrical and prorsiradiate ribs.
3. A. Davei nodosissimus is also continental. This variety shows nine large bullate tubercles on each whorl, with close, fine, and symmetrically disposed flexiradiate ribs.
1 Tgneous Rocks and their Origin, 1914, p. 212.
2 Tiacroix, Les Hnclaves des Roches Voleaniques, 1893, pp. 563-5.
5 A. Scott, ‘‘Pitchstones of South Arran’’: Trans. Geol. Soc. Glasgow, vol. xv, pt. i, p. 22, 1914.
4 Quenstedt, Die Ammoniten des Schwdbischenjura, 1885.
Sate
eee pS eee
GEOL. Mae., 1916. Pratr VIII.
G. F. Strawson, photo.
COELOCERAS DAVQI, RECTIRADIATUM, var. nov.
Lower Litas. GOLDEN Cap, Dorszr.
=
fp ey ie ree) t ‘y
e
lit
ane
t
Dr. Wyatt Wingrave—A New Variety of Ammonite. 197
Hitherto the first variety only has been described as of English source. Last year, on following the eastward continuation of the Green Ammonite Beds to Golden Cap several fragments of Davai were found in the Red Band. One of these supplies a nearly complete specimen, which does not conform to either of the above varieties.
It differs from 1 and 3 in several respects. The ribs are of finer texture, more numerous, never bifurcate, symmetrical in size and spacing, rectiradiate and showing no tendency whatever to a forward inclination, except the last few ribs near the aperture. In C. Davei the ribs are strongly prorsiradiate, unsymmetrical, and often bifurcate. The tubercles are much more numerous than in the orthodox Davez. They abruptly commence at the beginning of the penultimate whorl, and apparently adorn each rib as far as the inner- most whorls can be identified. In shape they are somewhat clavate, but not so prominent as in the ordinary Davav.
In the photograph several of the ribs on the outer whorls appear to indicate a tendency to tuberculation or ‘ flaring’; this is due to unremoved matrix. The suture has not yet been exposed, although an area of an inch or more of test was removed from the outer whorl near its termination, showing that the body-chamber, like other forms of Davei, is evidently a long one occupying more than one whorl.
The degree of involution is very slight, barely more than contact. Nearly the whole of the test is intact, and shows the characteristic russet colour of the matrix. (Plate VIII.)
Suggested name.— Ceeloceras Dave, var. rectiradiatum (var. noy.).
MorruotogicaL Drraits.
Size.—Diameter 80 mm.
Whorls.—Very slightly involute, polygyral (6), uncompressed, symmetrical increase in size and shape.
#ibs.—Numerous, single (never bifurcated), rectiradiate, shallow, regular interspaced, uninterrupted at venter.
Tubercles.—Numerous, small, clavate, on all the inner whorls, but outer whorl undecorated, non-septate.
Umbilicus.— Shallow, open (concentrum- and latumbilicate).
Venter.—Convex, cost uninterrupted.
Suture.—N ot exposed.
Distribution (source).—Red Band, Green Ammonite Beds, Lower Lias: Golden Cap, Dorset.
STRATIGRAPHY.
This specimen came from the ‘‘ Red Band ”’ of the Green Ammonite _ Beds, which at Golden Cap near Seatown forms its base, and is convenient of access from the beach. Below it is the well-marked ‘“White Band”, each having its attendant beds of clay. Here the limestone Red Band is scarcely 1 foot in thickness and occurs as a single layer, but Mr. Lang is of the opinion that further west it is probably double owing to weathering influences.! These beds yield a fair supply of Ammonites, chiefly in fragments among the clays.
1 Ww. D. Lang, ‘‘ Geology of Charmouth Cliffs’’: Proce. Geol. Assoc.; vol. xxv, pt. v, 1914.
198 Dr. Du Riche Preller—Crystalline Rocks of Piémont.
Above are otstoceras, T. Loscombet, below are latecosta and varieties of liparoceras. The Red Band itself yields Davei and various striata.
Complete specimens are confined to the limestone bands, for in the clays they are much. mixed and often only as fragments, casts, and moulds.
Oppel included practically the whole of the Green Ammonite Beds in his Davet zone; but in England this should be restricted to the Red Band, although fragments of Davei are often found in the clays several feet from the Red Limestone.
For the excellent photograph the writer is indebted to Mr. G. F. Strawson.
Ill.—Tar Crystattins Rock Arnas oF THE PIEMONTESE ALPs. I. Sournern anp Wersrern Prémont.
By C. S. Du RIcHE PRELLER, M.A., Ph.D., M.1.H.E., F.G.S., F.R.5.H.
InTRODUCTORY.
N continuation of the preceding paper (Gnor. Mae., April, p. 156) which, as a preliminary to the present one, outlined the new classification of the crystalline rock formations and the nomenclature of the pietre verdi of the Piémontese Alps, I now propose to briefly describe the principal pietre verdi areas with which I became familiar during a long stay on repeated occasions in Turin. This city, apart from its rich collections of the rocks and minerals of the Piémontese Alps, is a most central and convenient starting-point for examining the different valleys debouching into the plain of the Po from the magnificent crescent formed by the Maritime, Cottian, Grajan, and Pennine Alps, which, as seen from Turin, afford by far the most
extensive and fascinating Alpine panorama in Italy.
The principal pietre verdi areas lie more especially along or near the inner belt or concave eastern edge of the Alpine crescent, and include, among others, the following mountains and valleys which will be referred to in this and a subsequent paper, and all oe which form part of the watershed of the Po: —
Range. Mountain. Altitude. Valleys. | m. Maritime | Montgioie 2,836 |Bormida, Tanaro, Corsaglia, Tllero, Vermenagna. a Argentera 8,397 | Gesso, Stura di Cuneo. Cottian Monte Viso 83,843 |Grana, Maira, Varaita, Po, Pellice, Germanasca. Be Rocciavré 2,778 | Chisone, Sangone. Grajan Rocciamelone 3,537 | Dora Riparia (Susa Valley). fs Ciamarella 8,876 | Stura di Lanzo: Usseglio, Balme, and
Grande Valleys. “ Gran Paradiso | 4,081 | Orco, Soana.
Hf Grivola , 3,961 | Dora Baltea (Aosta Valley), Cogne, Valsavaranche. - Mte. Emilius |: 3,559 | Dora Baltea, Buthier, Valpelline. Pennine Mte. Rosa 4,636 | (Ivrea Belt) @hinsellay Dora Baltea, Tourmanche, Gressonay, Cervo, Sesia.
a a
Dr. Du Riche Preller—Crystalline Rocks of Piémont. 199
Fig. 1, SKETCH-MAP of Crystalline Rock Aréas in Piédmontese Alps
i (Southern and Western Piédmont.) i
: Tose GQ. Paradéso etek ean cra}
frees M.Cenis Y LY
| R.d'Ambin pe
in Te Z
rejus 7 CZ
~ 2S we
AS PNAS ‘ ly BA aurcore t,t ZZ Chabidke ra cs FZ
| soins SE
LolbikAZs “AViso BA
i
A ] nx. & nN be } w SoM Fo gene Mercarrtlo u : De orem ® Col
brenda
: f
PV = pietre-verdi; gn = gneiss; gr = granite; _ms = micCa-schist; cs a calc-schist ; P = Permian; T = Trias.
‘Scale 1: 1,100,000. . ‘Del. D.R.P.
200 Dr. Dw Riche Preller—Crystalline Rocks of Piémont.
Of the mountains enumerated, the Argentera and Gran Paradiso massifs, with a gneiss nucleus in each case, are the only ones which have preserved their original ellipsoidal, dome-shaped outlines, while most of the others, lying in the calc-schist and pietre verdi areas, are conspicuous pyramids whose precipitous flanks, pre-eminently those of Monte Viso and Grivola, were chiselled probably quite as much by atmospheric as by fluviatile or glacially abrasive action. The six principal pietre verdi areas, of which the first three will be dealt with in the present and the other three in a subsequent paper, are as follows :—
I. In Southern and Western Piémont: (1) the Maritime Alps; (2) Monte Viso; (3) the Dora Riparia, Sangone, and Avigliana group.
II. In Northern Piémont: (4) the Lanzo Valleys; (5) the Dora Baltea or Aosta Valley ; (6) the Lanzo, Ivrea, and Val Sesia group.
J. Tue Maritime Arps Group. (Fig. 1.)
1. Montgioie Range.—The pietre verdi area between the Ellero, Corsaglia, Tanaro, and Bormida Valleys on the north side of the Montgioie range derives special interest from the fact that the deposits occur in the Permian and Triassic crystalline formations, already described in a previous paper,’ while further east, towards Savona and near Voltri in Liguria, similar deposits are intercalated in Triassic schists, and further west, along the French frontier, they appear in the cale-schist formation. Proof is thus afforded that the pietre verdi are not confined to any particular horizon, but are associated with both Mesozoic and Paleozoic formations. Some of the pietre verdi deposits on the northern slopes of the Montgioie range were already mentioned by Zaccagna’”; but their number and extent has more recently been considerably increased by Franchi,? who
regards all the pietre verdi of the Ligurian, Maritime, and Cottian —
Alps as links in the same Mesozoic horizon.
The pietre verdi deposits between the Ellero, Tanaro, and Bormida Valleys, extending for about 30 kilometres along the lower hills from Villanova to Millesimo, are composed chiefly of lenticular masses of serpentinous, diabasic, and euphoditic rocks, the latter two largely altered to amphibolites and prasinites, all associated with Triassic crystalline and dolomitic limestone, in the Bormida valleys also with Permian schist, as already mentioned. In these, as also in the Lower Trias, occur frequent outcrops of laminated porphyric rock and masses of amphibolic schist often epidotic and garnetiferous, with abundant glaucophane.*
West of the Montgioie range, in the border zone of the Maritime and Cottian Alps, and notably in the upper Grana and Maira Valleys,
1 “The Permian Formation in Piémont, Dauphiné, and Savoy’’?: GEOL. MAG., January, 1916, p. 7 et seq.
2D. Zaccagna, ‘‘ Alpi Marittime’’: Boll. R. Com. geol., 1889, p. 395 et seq.
3 §. Franchi, ‘‘ Zona Pietre Verdi fra 1’Ellero e la Bormida, Alpi Marittime ’’: ibid., 1906, p. 89 et seq.
4 The nomenclature used throughout this paper is that given in the preceding one, GEOL. MAG., April, 1916, pp. 156-63.
ee eee -
; : F
Dr. Du Riche Preller—Crystalline Rocks of Piémont. 201
similar euphoditic and diabasic masses occur in the calc-schist forma- tion, but intensely metamorphosed, the former to epidotic and chloritic prasinites with or without gastaldite (blue secondary hornblende), the latter to felspathic prasinites and amphibolites.' These pietre verdi masses bear close analogy to the euphoditic and diabasic, also variolitic masses with overlying serpentine in the cale-schists of Maurin and of the Chabriére Valley, near Pointe de Mary, about 30 kilometres further north-west, as also to those of the Mont Genévre group another 30 kilometres further north, and to those between the Ripa and Troncéa Valleys about 20 kilometres east of Genévre. From the occurrence of all these crystalline masses both of eruptive? and sedimentary origin on the northern and eastern flank of the Permian horizon, Franchi has rightly concluded that that formation separates the Trias into two distinct zones: an external one on the left, composed of the ordinary, fossiliferous limestone, gypsum, and cargneules or Briangonnais facies, and an internal zone, the crystalline and semi- erystalline facies composed of the cale-schists and crystalline and dolomitic limestone with pietre verdi.*
2. The Argentera Massif (Fig. 1).—This massif, also called Mer- eantour, is an oval-shaped ellipsoidal group of 60 by 25 kilometres in approximate length and width, extending west of Col di Tenda along the French frontier, and bordered on the north by the Stura di Cuneo Valley, which separates the Maritime from the Cottian Alps. The massif includes, besides Monte Argentera (3,397 m.) and Monte Matto (3,057m.) in the centre, some of the highest mountains of the Maritime Alps, e.g. Mercantour (2,775m.) and Monte Clapier (3,046 m.) at the south-eastern, and Monte Tinibras (3,032 m.) at the north-western end. The access to the central part is by the Gesso Valley from Valdieri, whose well-known hot sulphur springs rise in the upper valley, at 1,346 metres altitude, almost in the centre of the massif. The latter is, like the Dora-Maira and Gran Paradiso gneiss massifs, entirely free from pietre verdi on its surface; even the fringe of pietre verdi which surrounds those massifs is absent on its periphery. Zaccagna attributes this isolation of the Argentera massif to a great fault along the Stura Valley, which latter is, some 20 kilo- metres north-east of Valdieri, crossed by a succession of pietre verdi outcrops descending from the Maira and Grana Valleys towards Cuneo and S. Dalmazzo, and thence running along the base of the Montgioie range to Villanova and Millesimo.
The Argentera massif consists, in the main, of three crystalline formations: a nucleus of primitive, glandular, large-grained, granitoid,
1 §. Franchi, ‘‘ Aleuni Metamorfisi di eufotidi e diabasi Alpi Occid.’’: Boll. R. Com. geol., 1895, p. 181 et seq. The transformation described in this important memoir applies equally to similar phenomena in all the other pietre verdi areas of the Piémontese Alps. In the massive and schistose amphibolites of the Grana and Maira Valleys, as also in Val Chisone, at Pegli, Liguria, and in the Tuscan archipelago, Franchi found the equivalent of the Californian mineral lawsonite, a secondary pseudomorphic plagioclase corresponding to the formula of hydro-anorthite felspar (Boll. R. Com. geol., 1898, p. 308).
* The term ‘ eruptive’ is used in this paper in preference to ‘igneous’ as better corresponding to the non-intrusive character of the Piémontese rocks.
202 Dr. Du Riche Preller—Crystalline Rocks of Piémont.
and eye-gneiss;1 a large area, about 12 by 10 kilometres, of granite intrusive in the gneiss nucleus; and asurrounding belt of great masses of small-grained gneiss and mica-schist. The primitive gneiss, and to a much lesser extent also the intrusive granite is traversed in all directions by countless thin veins of acid rocks, chiefly microgranite, aplite, quartziferous and hornblendic porphyrite, while the outer eneiss contains intercalated masses of both augitic and hornblendic diorite and of compact serpentine. These rocks, being here intimately associated with gneiss, are not pietre verdi with secondary elements ; but they show that the prototypes of the latter are not wanting even in the more ancient crystalline series.
Professor Sacco regards the position of the gneiss and granite of the Argentera massif as reversed, viz. the granite not as intrusive, but as constituting the nucleus of the massif, enveloped by an enormous mass of gneiss intensely metamorphosed and of Permo-Carboniferous age*; but Franchi’s interpretation * is no doubt correct, the more so as there is no passage from gneiss to granite, and the intrusive character of the latter is beyond question. Moreover, the Triassic beds on the eastern as well as the Permian on the southern periphery of the massif overlie the gneiss with marked unconformity, thus pointing to a long interval of deposition and therefore to a considerable difference of age between the gneiss and the overlying younger formations.
IJ. THe Monre Viso Grove. (Figs. 1 and 2.*)
This area forms an elongated lenticular ellipsoid from south to north, about 40 kilometres in length and 2 to 6 kilometres in width, between the Maira Valley at its southern and the Pellice Valley at its northern end, while nearer the centre on its southern side it is cut by the Varaita Valley. In the centre itself, on the eastern side, rises the Po, which, although in its lower course it collects the drainage of all the rivers of the Piémontese Alps, is, in its upper torrential and cascade course, the shortest of all.
1 The term ‘ primitive’ gneiss is used throughout this paper in its strictly stratigraphical sense as the ‘fundamental’ substratum of all the more recent formations.
2 F. Sacco, ‘‘L’Age du massif de l’Argentére’’: Bull. Soc. géol. France, 1907, vi, p. 484 et seq. Also ‘‘Gruppo dell’ Argentera’’: Mem. R. Acc. Scienze, Torino, 1911, lxi, p. 457 et seq.
3S. Franchi, ‘‘ Osservazioni lavori geol. Alpi Marittime’’: Boll. R. Com. geol., 1907, p. 145 et seq. Among the excellent reports in the Boll. R. Com. geol., besides those already quoted in this and the preceding paper, are the following relating to the Cottian Alps :—
8. Franchi, ‘‘ Tettonica della zona pietre verdi del Piemonte,’’ 1906, p. 118 et seq.; ‘‘ Appunti geol. e petrogr. Monti di Bussoleno,’’ 1895, p. 3 et seq.
S. Franchi and V. Novarese, ‘‘ Appunti geol. e petrogr. dintorni di Pinerolo,’’ 1895, p. 385 et seq. \
V. Novarese, ‘‘ Rilevamento geol. Valle Germanasca,’’ 1895, p. 253 et seq. ; ‘“Rilevamento geol. Valle Peliice,’’ 1896, p. 231 et seq.
A. Stella, ‘‘Rilevamento geol. Valle Varaita;’’ 1895, p. 283 et seq. ; ‘* Rilevamento geol. Valle Po,’’ 1896, p. 268 et seq.
4 Figs. 2-4 will appear in the next part of this paper in June.
Dr. Du Riche Pretler—Crystalline Rocks of Piémont. 203
The majestic appearance of Monte Viso—Pliny’s Mons Vesulus—is largely owing to the surrounding area of calc-schists having been considerably lowered by erosion which scooped out a socket-like depression round the base of the more resistant pietre verdi mass, and thus made the pyramid—the highest point of the Cottian Alps—all the more imposing. Close to it rise two similarly shaped but lower spurs: Visomut on its eastern side, and Visolotto grafted on its western flank, all three being in their upper or pyramidal parts composed entirely of pietre verdi. The same applies to Colle delle Trayersette (3,287 m.) at the western, to Monte Granero (3,170 m.) at the northern, and to Lobbie di Viso (2,990 m.) at the southern end of the group, which thus forms an enormous lenticular mass in the cale- schist formation, parallel to the Dora—Maira gneiss massif which separates it from the Po plain.
1. The Pretre Verdi Area of Monte Viso.—The least difficult access to the central part of the group for examining the pietre verdi series is from Barge (500 m.) to Paesana and thence up the Po ravine to Crissolo (1,385 m.) and to the summit of Monte Viso (3,843 m.), the four stages being (1) the eastern mica-schist zone to Paesana; (2) the Dora—Maira gneiss massif, in the ravine or chiusa of which the Po is joined by the torrent Lenta; (3) the western mica-schist, and then the predominant cale-schist formation with the quarried crystalline limestone beds of Crissolo; and (4) the pietre verdi up to the summit.
The base of the Visomut spur discloses a great bank of serpentine. passing to schist, at least 500 metres in thickness, followed to the top by alternating banks of gneissiform euphodite and enphoditic and amphibolic schist, the former conspicuous by smaragdite, the latter by its epidotic veins, both of which minerals are largely prominent throughout the whole Monte Viso group. The depression between Visomut and Monte Viso, in which are embedded Lago Grande and other tarns, is composed of calc-schist, chloritic and serpentinous schist. From this point the succession of pietre verdi banks can be traced uninterruptedly to the summit of Monte Viso along the path leading from the Quintino Sella refuge (about 3,000 m.) up the southern flank. From the refuge, which is built on a felspathic euphodite bank, to the summit, the flank presents a series of alternating banks—as shown in the section, Fig. 2!—of euphodite, epidotic, amphibolic, actinolitic, and prasinitic schists from 200 to 300 metres in thickness, with smaller intervening banks of serpentinous schist. The euphodite, varying from compact to schistose, is largely of porphyric texture with greyish violet felspar and diallage altered to smaragdite. The amphibolic and prasinitic schists and their varieties predominate largely, and, together with euphodite, constitute the summit of Monte Viso, as they also do that of the almost perpendicular
I This section is founded on Zaccagna’s great transverse section west to east of 70 kilom. from St. Paul in Dauphiné through the cale-schist formation, Monte Viso, and the Dora—Maira massif to Rocca Cavour in the Po Valley (Boll. R. Com. geol., 1887, p. 416, tav. ix). Franchi gives a similar section of the Monte Viso group at a lower level further south (ibid., 1898, p. 482, tay. ix; also Stella, ibid., 1896, p. 288). (For Fig. 2 see June Number.)
204 Dr. Dw Riche Preller—Crystalline Rocks of Piémont.
peak of Visolotto. In all the alternating banks the gradual passage into, and compenetration with each other is very marked, and-so is more especially the tendency to chloritic decomposition forming serpentinous schist, which in contact with narrow bands of crystalline limestone imparts to the latter its greenish colour.
The descent from Monte Viso may, on the southern side, be conveniently effected by the Forciolline gorge, and thence through the Vallante ravine and the Varaita Valley by Sampeyre and Venasca to Saluzzo in the Po Valley. In those deeply eroded ravines the calc-schist formation reappears in contact with amphibolie, prasinitic, and serpentinous schist. At the junction of the Vallante and Varaita Valleys the last-named schist predominates, and lower down the latter valley is replaced by alternating banks of cale-schist, serpentine, and chloritic amphibolite.
2. The Gneiss, Mica-schist, and Graphitic Area.—Parallel to and east of the pietre verdi area of Monte Viso runs, as already mentioned, the Dora—Maira primitive gneiss massif, about 60 kilometres in length and 5 to 10 kilometres in width, at an altitude of 1,500 to 2,000 metres, the visible thickness being about 700 to 1,000 metres. Its superficial continuity is, however, frequently interrupted by great intervening, overlying, or intercalated masses of minute, granular, and tabular gneiss, with which are associated masses of erystalline limestone, quartzite, steatite, and dioritic, amphibolic, and prasinitic rocks. ‘he primitive gneiss is the typical rock with large elements, glandular, often granitoid, and tourmaliniferous; the mica- schists, often garnetiferous, and the minute, tabular gneiss flank the primitive gneiss both on the eastern and western side. Of the gneissoid dioritic rocks associated with the minute and tabular gneiss, which latter reaches, e.g. in the Pellice Valley, a thickness of 1,500 metres, an intercalated mass 700 metres in thickness occurs near Barge; another, 1,000 metres, near Angrogna (Pellice); and again, in the Chisone Valley, another 1,500 metres in thickness, where the dioritic rock is associated with and altered to amphibolites and prasinites, including the ovardite of Fenestrelle. Both the tabular gneiss and the crystalline limestone, often associated with steatite, are extensively quarried on the eastern side of the Dora—Maira massif, at Vernasca, in the Varaita, near Luserna, in the Pellice, and near Malanaggio, etc., in the Chisone Valley, as are also the fissile, tegular, quartzite masses (bargiolina) of Monte Bracco (1,305 m.) near Barge.
In the same mica-schist and minute gneiss horizon occur masses of graphitic rock with intercalations of graphite, which, flanking Monte Bracco on its western side, extend about 20 kilometres south, and about the same distance north of Barge. It is here, in the Pellice and Chisone Valleys, that the graphitic zone is. associated with the gneissoid dioritic rocks already mentioned. The whole mica-schist, minute gneiss, graphitic and dioritic zone is now assigned to the Permo-Carboniferous.
3. Summary.—Vhe Monte Viso and Dora—Maira areas may be grouped, in ascending order from east to west, viz. from Barge in the Po Valley to Crissolo and the summit of Monte Viso, in a distance of 20 kilometres, in four horizons as follows :—
Leonard Hawkes—Tridymite in Icelandic Rocks. 205
Visible Altitude. depth.
I. Primitive gneiss of Dora—Maira massif, glandular to granitoid II. Miea-schists, minute, tabular, and graphitic | 500-2,000 1,500
eneiss with quartzite, crystalline limestone,
steatite, graphite, and dioritic rocks III. Cale-schists with crystalline limestone, pes
and amphiboliec schists . z . 1,300-2,000 700 IY. Pietre verdi to summit of Monte Viso; : " serpentine
and serpentinous schist ; epidotic amphibolites ;
glaucophanic prasinites ; actinolitic, chloritic, - 2,000-3,800 1,800
and taleose schists; euphodites, gneissiform,
porphyritic, and schistose
3,300 The total visible thickness between the extreme points—exclusive of the fall of level in the depression between the gneiss massif and the calc-schist horizon on the western flank of the former—is thus 3,300 metres.
The fact that the mica-schist horizon flanks the gneiss massif on both sides, but on the eastern side along the base, viz. at a lower level, led Gastaldi to regard this reversal of the normal sequence as evidence of a zonal subsidence (sprofondamento), the more so as both formations dip below the valley floor and reappear about 6 kilometres east in the isolated outcrop of Rocca Cavour (460m.). Zaccagna, on the other hand, explained the phenomenon as an anticlinal retroflex fold of the gneiss massif from west to east. As a zonal fracture or subsidence, it bears close analogy to similar zonal phenomena in Northern Piémont, to which I shall refer in the sequel.
(To be continued in our next Number.)
IV.—On Trivymire and Quarrz arrer Trrpymire in IceLanpic Rooks. By LEONARD HAWKES, B.Sc. (PLATE IX.) LACROIX in his researches on volcanic rocks and their inclusions . has shown that tridymite occurs in two distinct forms, each produced under special conditions. ‘‘ Il est important de constater dans un méme échantillon l’existence de tridymite produite par deux modes de genése distincts ; qui lui ont imprimé deux formes différentes. L’une Welles est caracterisée par des cristaux épais, a macles binaires, elle a été formée par fusion; l’autre se présentant en lamelles ex- trémement minces, empilées a été produite par action pneumatolytique. Cette variété de tridymite constitue le dernier des minéraux dr rusiques formés, et elle résulte trés probablement de l’attaque a haute température dun résidue de matiére vitreuse trés siliceuse dont des restes peuvent étre parfois encore constatés directement’ (1, p. 387). Both forms occur in Icelandic rocks. In his description of the liparite of Hlidarfjall, Backstrom notes ‘‘sehr schonen Tridymite als letzte Bildung” (2, p. 661). Through the kindness of Professor Backstrom I was enabled to examine his
206 Leonard Hawkes—Tridymite in Icelandic Rocks, —
rock sections, and a microphotograph showing the characteristic form of the tridymite is given in Fig. 1. The crystals are thick and frequently show binary twinning after (018). ‘Their resemblance to the artificial tridymite from the bricks lining the glass furnaces of Appert, Clichy, in France is obvious (ef. Fig. 2, 1, p. 331). The commoner form of tridymite, that of thin tables, is well shown in a breccia from Faskrudsfjord, East Iceland, consisting chiefly of fragments of an acid rock embedded in acid volcanic ash. This rock, 80 feet in thickness and intercalated in the Tertiary basalts, is exposed on the shore about a mile east of the town. The fragments of ash and lava contain phenocrysts of soda-microcline and soda- pyroxene in (a) a glassy perlitic base and (b) an aggregate of felspar quartz and pyroxene grains, respectively. In (a) the perlitic ground- mass is often weakly anisotropic, being made up of thin plates of tridymite. In (6) similar tridymite occurs together with quartz (described below) in cavities, and apparently in the groundmass. The nature and mode of occurrence of the two forms of tridymite of Hlidarfjall and Faskrudsfjord are in full accord with the theory of their mode of origin advanced by Lacroix.
Quarts after Tridymite.
The quartz to be described occurs in the rock of Faskrudsfjord. The pseudomorphs are of two types, both originating from the thin tabular form of tridymite.
Type I.—Previously noted by Mallard (8, p. 162), Lacroix, and Geijer (4). The holocrystalline fragments of the Faskrudstjord breccia contain cavities filled with quartz, chlorite, and a small amount of a feebly double refracting mineral of low refraction, probably tridymite. A microphotograph of a cavity is given in Fig. 2. The quartz is of peculiar habit, forming a complex of lamellee branching out from one another at different angles. The network of laths in the cavity illustrated in Fig. 2 is comprised of two individuals, distinguished optically. While several lamellae may form one individual of common optical orientation, the laths forking without change in optical properties, one straight lath may be composed of many individuals. Fig. 3 shows another assemblage of laths comprising five individuals. This quartz is undoubtedly a paramorph of tridymite, and Geijer has described a similar occurrence in cavities in a pre-Cambrian quartz porphyry found as boulders in a moraine on Gotland. (See especially the photograph on p. 71, 4.) The quartz of the holocrystalline groundmass of the Icelandic rock is micropoikilitically developed, and without going into the question of micropoikilitic reticulating quartz which has been discussed by Geijer, it may be stated that it too, judging from its occurrence and association, is very probably a pseudomorph of tridymite. It is interesting to note that the soda-microcline pheno- erysts, which typically show inclusions of glass, sometimes contain lamellar quartz after tridymite (see Fig. 4), thus indirectly supporting Lacroix’s theory of the formation of tabular tridymite, ‘‘ de l’attaque & haute temperature d’un résidue de matiére vitreuse trés siliceuse.”
Type II.—The paramorphs of Type I are characterized by the
Leonard Hawkes—Tridymite in Icelandic Rocks. 207
retention of the lamellar form of the tridymite. In those now to be described the outline of the quartz is not that of the tridymite lamelle, being more or less rounded. ‘This type is well illustrated in a fragment 1 mm. in diameter, composed of twenty-three variously sized quartz grains, embedded in the Faskrudsfjord rock. Fig. 5 is a microphotograph of a part of the fragment, and Fig. 6 shows its outline and that of its component individuals. The quartzes are allotriomorphic with respect to one another, and a rapid glance conveys the impression of the usual granitic texture. On closer investigation, however, they are seen to have straight lines running
Fic. 6.—A drawing of the aggregate of Fig. 5. The dotted lines are the traces of the former tridymite lamelle. through them, commonly in pairs, giving a rod-like appearance. Some of these lines are very distinct with a medium magnification, and they can be seen in Fig. 5, but many of them are only discernible using a high power and after continued observation. The lines discovered are dotted in in Fig. 6 ; none could be found in some of the quartzes. The structure is seen on slight movement of the microscope tube. The lines are dark and accompanied by ‘ white lines’, those forming a ‘pair’ or ‘rod’ deflecting in the same horizontal direction on movement of the tube. The lines obviously represent planes or cracks, each pair having a common inclination to the plane of section.
208 Leonard Hawkes—Tridymite in Icelandic Rocks.
Sometimes several parallel lines have a common inclination clearly representing a section cut across several parallel imbricated lamelle. Tke lamelle join at varying angles, their junction often coinciding with that of the quartz individuals; though two joined lamelle may be contained in one individual. In one case three parallel lamelle of one quartz are joined at an angle to three parallel lamelle of an adjoining quartz, at the line of junction of the two individuals. Again, one straight lath may be contained in two quartzes. The lamellas commonly have a line of dark dust inclusions along their middle or surface. In general there is a tendency to coincidence in direction of the lamelle and the length direction of the quartz individuals. Fig. 7 is a drawing illustrating another homogeneous quartz filling a cavity and showing traces of a former complex of tridymite tables.
Fic. 7.—Drawing of a single quartz individual, showing traces of an original complex of tridymite lamelle. x 150.
It is clear that this granular quartz of 'ype II is merely a further evolution of that of Type I. Taking the lamelle in the granular quartz by themselves, their morphological and optical characters exactly correspond to those of the tabular quartz of Type I. In a complex of tridymite lamelle the paramorphism to quartz begins in certain of them, many going to form a single individual or one being changed into several, producing the structure of Type I. A further step is the paramorphism of the tridymite occupying the interspaces between these laths, and, probably through inoculation, the quartz formed is in optical continuity with that already present, giving rise to homogeneous granular individuals. The quartz shown to the left in Fig. 2 is obviously in the transition stage between the two types. The laths are the scaffolding on which the granular individual is moulded.
The question arises as to whether we have been correct in regarding all granular quartz in igneous rocks as primary. The evidence is quite conclusive that the quartz individuals of Type IL in the Faskrudsfjord breccia are paramorphic after tridymite, yet in some of them the tridymite structure is only discernible with considerable difficulty, and in a few it is entirely eradicated. The importance of this fact in questions concerning the temperature of crystallization of quartz is obvious, and whilst it is unlikely that much granular quartz has originated from tridymite in the way
Grou. Maa., 1916. Pratt IX.
Fig. 5. Fic. 4.
TRIDYMITE AND QUARTZ IN ICELANDIC ACID ROCKS.
1
F Kingdon Ward—The Land of Deep Corrosions. 209
described, it is desired to draw the attention of petrographers to the structure, in the hope of finding it to be of wider occurrence.
In quartz-porphyries with micro-poikilitic structure the quartz phenocrysts are often surrounded by a network of quartz laths in optical continuity. Geijer regards the laths as paramorphic after tridymite, and suggests that their optical continuity with the phenocrysts may be due to inoculation by the latter. The discovery of the granular quartz suggested the possibility of these phenocrysts themselves being paramorphs of tridymite, and through the kindness of Professor P. D. Quensel, of Stockholm, I was permitted to look through Dr. Hedstrom’s slides described by Geijer. There were no traces in the phenocrysts of any structure similar to that in the Faskrudsfjord rock. Unfortunately there are no quartz phenocrysts in the Icelandic rock, and it is impossible to speak definitely yet on the question of phenocrysts and micropoikilitic quartz.
I wish to express my thanks’ to Professor W. C. Brogger for permission to work at the Mineralogical Institute of the University of Christiania, and to Professor V. M. Goldschmidt for help and advice.
REFERENCES. 1. A. LAcRorx, ‘‘ pat la tridymite du Vésuve et sur la genése de ce minéral par fusion ’’: Bull. Soc. Fr. Min., xxxi, 1908. hele Peay ‘“‘ Beitrage zur Kenntnis der islandischen Liparite’’ : Geol. Foren. Férhandl., No. 140, Bd. xiii, 1891. 3. MALLARD, Bull. Soc. Fr. Min., xiii, 1890. 4, P. GuigER, “ Poikilitic Intergrowths’’: Geol. Féren. Férhandl., Bd. xxxiv, Heft i, 1913. EXPLANATION OF PLATE IX. Fig. 1.—Nicols crossed. Section of the Hlidarfjall Liparite (Professor - Backstrém’s collection), showing an assemblage of thick twinned tridymite crystals. x 40 ,, 2.—Nicols crossed. Section of a fragment in the Faskrudsfjord rock, showing typical development of quartz lamelle—paramorphs of tridymite—in a cavity. The lamelle comprise two quartz individuals. The light streaky patches in the groundmass are micropoikilitic quartz. x 40. », °%.—WNicols crossed. Section showing a complex of quartz lamelle— paramorphs of tridymite—in a cavity in a fragment of the Faskruds- fjord rock, and optically resolvable into five individuals. x 120. ,, 4. Nicols crossed. From the Faskrudsfjord rock, showing a phenocryst of soda-microcline with albite and pericline twinning, and holding as an inclusion quartz lamelle, paramorphs of tridymite. x 120. ,, 98. Nicols crossed. From the Faskrudsfjord rock. Shows an aggregate of quartz grains with traces of tridymite lamellar forms. x 120.
V.—Fortuer Groroetcat Nores on tHe Lanp or Drsp Corrostons.' By F. KINGDON WARD, B.A., F.R.G.S. N the Grotoercan Magazine for April, 1913,” I drew attention to certain features of the country forming the Yunnan—Tibet border. Further travels there in 1913 and through the Burmese hinterland 1 in 1914 enable me now to supplement and ‘extend those notes.
1 The rock specimens collected during my journeys of 1913 and 1914 have not been described. Their examination may help to throw some light on the problems here indicated.
2 ** Geological Notes on the Land of Deep Corrosions,’’ pp. 148-53, Pls. V and VI.
DECADE VI.—VOL. III.—NO. V. i 14
210 F. Kingdon Ward—The Land of Deep Corrosions.
Many travellers crossing Western China between Burma and Ssuchuan have regarded the endless parallel ranges which have to be erossed as spurs thrown out from the main Himalayan range or from the Tibetan plateau, at least as far south as Likiang. Thus Captain Gill writes: ‘‘The great plateau that extends over the whole of Central Asia throws down a huge arm between the Chin-sha-chiang (Yangtze) and the Lan-tsang-chiang (Mekong), gradually diminishing in altitude as it extends south. The northern portion of this arm partakes more or less of the character of the main tableland . . . this arm is not more than 35 miles wide in the latitude of Batang and . . . it is little more-than a ridge of mountains running due north and south between the two streams” (Zhe River of Golden Sand, vol. ii). West of Batang the summit of this divide is, as Captain Gill indicates, an undulating grass-land plateau cut up by streams flowing in shallow valleys, with lakes occupying hollows here and there, from 12,000 to 14,000 feet above sea-level; in appearance it closely resembles the grass-land country of North-East Tibet, on the Kansu border. But trom Atuntsi southwards to Likiang the divide narrows down to a mere rock wall.
However, it is inconceivable that the Mekong—Yangtze divide was formed independently of the Mekong—Salween and Salween—Irrawaddy divides, which so closely resemble it in structure, as well as in their flora; if the Mekong—Yangtze divide is an arm of the great plateau, or a spur of the Himalayas, so too are its immediate neighbours, the Mekong—Salween and Salween-Irrawaddy divides.
The same characteristics are repeated throughout the country to the east of Batang, though in a less sensational manner. The whole of the immense mountainous region lying between Batang and Tatsienlu and between the parallels of 32° and 26° partakes of the same nature, and though I do not know it at first hand the accounts of the few travellers who have been there emphasize the fact that it is a region of high parallel mountain ranges, often snow-clad, trending north and south, with rivers flowing south in deep narrow valleys between. However, in all this country there is no river to compare with those of the Yunnan—Tibet border, the Yalung being the only one of any size, though even beyond Tatsienlu the T'a-tu, and beyond that again the Min, also flow south.
Captain Gill says of the country between Tatsienlu and Batang the day after leaving the former city: ‘‘ A few yards more, and reaching the summit of the Cheh-toh-shan we at length looked upon the great Himalayan plateau . . . and from this point, with the exception of a dip into the Yalung-chiang, the road is always at an altitude of 12,000 feet above the sea until the descent into the valley of the Chin-sha-chiang . . . ” (Zhe River of Golden Sand, vol. i1).
The object of the present paper is to insist on the relationship and common origin of the physical features of the entire region from the Brahmapootra in Assam, across the sources of the Irrawaddy in the Burmese hinterland and the Yunnan—Tibet border, into Western China. There is no reason whatever to believe that this region may be regarded as a dissected plateau—that it was uplifted in its entirety at the same time as the Tibetan plateau and subsequently dissected
F. Kingdon Ward—The Land of Deep Corrosions. 211
by rivers all flowing in one direction, leaving parallel mountain chains between. Why do the rivers all flow in one direction? Moreover, there is a significant curiosity about the courses of some of these rivers. The main lines of drainage run due south, parallel to the great ranges, since they cannot as a rule flow across them (hence the ranges antedate the rivers, or are perhaps contemporaneous with them). But why should the tributary streams throughout their greater lengths flow strictly parallel to the main rivers, finally turning abruptly at right angles to join them? This is true of the tributaries of the Mekong and Salween, and is even more pronounced in the case of the ’Nmai-hka. The explanation, I think, lies in the fact that the region is traversed by parallel lines of weakness, produced in a manner to be described presently, and it will probably be found that the tributaries turn at right angles to join the main rivers where a change in the character of the rocks occurs.
Of the parallel rivers, the Mekong is the most easterly that continues its southern course to the sea. The Yangtze, after a series of remarkable loops, turns away to the east, thus snapping up all the rivers beyond which flow southward, and it has been suggested that it too, like the Mekong and Salween, once had an outlet to the south, through Indo-China. On what evidence that supposition is based I do not know, but a valley or series of valleys running southwards from Likiang, where the Yangtze abruptly ceases to flow southwards, to Tali-fu, now occupied by a chain of lakes and marshes draining south to the Mekong, of which the Tali-fu Lake itself is by far the most conspicuous, lends colour to the suggestion; there are also hot springs all the way along this shallow depression, and records of numerous earthquakes, leading to the belief that considerable crust movement has taken place here. The rocks are mainly sandstones, shales, and lhmestone—crystalline on the Tali-fu range.
The big N-shaped bend of the Yangtze, at the end of its southern journey, just before it definitely sets out eastwards towards the Japan Sea, in the course of which it cuts diagonally across the Likiang range, not flowing round it as is shown on the maps, is peculiar, but by no means unique in this region. Here I need only remark that the fact of the river cutting across the range suggests that this portion of that river at least existed prior to the uplift of the lofty Likiang range; but it was not then necessarily the source stream of the Yangtze as we now understand that river. It is much more likely that the Chin-sha-chiang (reserving this name for the southward- flowing upper portion of the Yangtze) did actually continue southwards past Likiang, being subsequently beheaded by the upper course of the eastward-flowing portion cutting back westwards; the southern portion of the Chin-sha-chiang, being thus isolated from its source, ultimately disappearing. This would account for the abrupt change of direction of the Yangtze, but not altogether for the extraordinary double loop into which it bends itself, unless we suppose that the western loop was originally a tributary of the independent Chin-sha, the water of the latter being eventually diverted through the channel of the former to join the Yangtze. At any rate this peculiarity is shared by at least three other rivers of
212 F. Kingdon Ward—The Land of Deep Corrosions.
this region, namely, the Yalung, the Dayul River (or Wi-ch‘u), and the Ngawchang-hka, while the upper portion of the ’Nmai-hka attempts a similar evolution and achieves a double bend, each half of which is less than a right angle. By the pinching of the rivers between rocks subjected to two sets of earth mevements acting at right angles to each other, in some cases actually buckling the strata, and to cutting back, owing partly to differences of rainfall on the two sides of a mountain range and partly to differences of level and of grade in the river-beds, which has gradually brought rivers originally belonging to separate hydrographic systems into contact, I imagine the whimsical courses of these rivers to have been evolved from simple courses. Whether this explanation be right or wrong, there can be no doubt that the several rivers which exhibit this phenomenon of reversed flow owe it to a common cause, and not to some chance freak in each case.
It may be asked, what became of all the rain-water which must have fallen on this country previous to the west to east movement which, by cutting across and breaching the long axis of the great Asiatic divide, allowed the parallel rivers to drain southwards? ‘The answer is, much of the region was then occupied by vast lakes into
which the water was poured. In the case of Hkamti—Loong, to be.
referred to presently, at the sources of the Mali-hka (or western branch of the Irrawaddy), it is sufficiently obvious that this plain was once occupied by a lake, and again much further east we have an . ancient lake bottom in the ‘red basin’ of Ssuchuan, now the fertile Chengtu plain. But there is proof in the sandstones, slates, and lime- stone of the border country itself that most. of it was once under water. Much of the Mekong—Yangtze divide, for instance, is capped by limestone now raised 18,000 or 20,000 feet above sea-level, and the same rock reappears on the ranges to the west. North of Likiang we cross plateau country partially occupied by insignificant lakes, surrounded by sandstone or limestone ranges from the bases of which well up hot springs. But whereas the Hkamti plain is only 1,200 feet above sea-level, with parallel ridges of sands and clays enclosing organic remains still intact, rising 3,000 or 4,000 feet higher in the south, the old sea or lake bottoms east of the Yangtze have been pushed up into plateaux 8,000 to 12,000 feet above sea-level, and regional metamorphism must have obliterated any organic remains which may once have existed. Whereas the isolated lakes of Tibet are drying up, those of the Yunnan—Tibet border country have been drained.
As already remarked, this border country has, in my opinion, been subjected to two sets of crust movement acting approximately at right angles to each other in such a manner that the hydrographic system set up during the first phase, at a later period became involved with and largely obliterated by that resulting from the second phase ; further complications were gradually introduced by the cutting back of either the primary or the secondary rivers, but especially by the former, according to local circumstances. During the first phase the Himalayas and the main backbone of China, separating the Yangtze and Yellow River basins, were raised up; during the second,
a
ae ae ae a
F. Kingdon Ward—The Land of Deep Corrosions. 2138
the north and south trending parallel ranges which lie between Assam and Western China, though the Himalayas may have and probably did receive their last and greatest uplift (in Tertiary times) at a subsequent date.
During the period of the first phase the region we are considering may have appeared somewhat as follows: (1) The Himalayas, either continuous with, or at least throwing out spurs to, the main divide of China (a consideration of the distribution of plants on the Himalayas and in Western China leads to this conclusion). (2) A great lake or system of lakes stretching throughout the present headwaters of the Mali-hka westwards into Assam, and covering thousands of square miles. (3) A region of great lakes and volcanic activity in Western China. (4) A number of rivers flowing into these rivers from the west, of which the upper courses of the Brahmapootra and Salween may have existed more or less as at present, eventually becoming involved with rivers consequent upon the second phase.
At this time the Irrawaddy can have had no existence, nor probably had the Mekong. The Yangtze, however, flowed eastwards from the neighbourhood of the Chengtu plain, then a vast lake; its present upper course (distinguished as the Chin-sha-chiang) did not exist, and the same applies to the lower course of the Salween.
The second great phase now seems to have been initiated by a crust movement from west to east, accompanied by the irruption of vast masses of granite. It may be thata lateral shifting of the Himalayan axis eastwards accounted for this, or perhaps it was due to a natural shrinking and settling of the crust; but whatever the cause, the parallel ranges to the east were those first formed, the western ones being pushed up later (the glacial phenomena and the distribution of flora on the parallel divides show this).
The result of this second earth movement was to break the continuity of the Sino-Himalayan axis, and start rivers flowing southwards through the breach. Thus arose the Mekong and the lower course of the Salween from about latitude 29°, while the draining of the Hkamti-Assam country gave rise to the Irrawaddy. At this time too the Chin-sha may have flowed southwards past Talifu to the sea through Indo-China. The parallel divides were then much lower than at present, and the monsoon rains swept on into Western China, where there were great glaciers. Meanwhile the rivers of the old system were rapidly cutting back, with the result that the Yangtze eventually tapped the Chin- sha, while the lower and upper courses of the Brahmapootra, cutting down as the Himalayas rose, became united. All this time the parallel divides were being slowly elevated, gradually pushed up one by one from the west, but the probability is that they had attained no great elevation till the present hydrographic system was established, and there is reason to believe, from a consideration of the glacial phenomena on the Mekong-Yang gtze and Mekong—Salween Tease matter which requires separate treatment—that they are still rising.
I have stated my belief that the parallel divides, with their intervening valleys, were formed by pressure from the west—that is to say, that the region is a series of anticlines and synclines; and on
214 F. Kingdon Ward—The Land .of Deep Corrosions.
the whole it appears to be so. But the gorges in which flow the ’Nmai-hka, Salween, Mekong, and Chin-sha are not simple synclines deepened by erosion; they are more in the nature of rifts, gashes, or possibly faults produced by some other agency.
If we cross all the valleys and mountain ranges, starting from the Brahmapootra, and travelling eastwards, keeping always in the same latitude, we shall find that as we pass from one valley to the next, we are gradually ascending, and also crossing successively higher mountain ranges between them, till the maximum average height is reached on the divide separating the Mekong from the Chin-sha for the short distance these rivers flow parallel to one another. The Mekong—Yangtze divide, however, is not the most snow-clad, for being protected from the monsoon by rain-screens to the west it receives only a fraction of the precipitation which falls on the western ranges, exposed to the full onslaught of the monsoon. Thus the entire region from the Brahmapootra to the Yangtze, in about latitude 28°, presents the appearance of a hugh bulk of rock, crystalline in the east, inclined from west to east, and trenched, riven, split asunder again and again from north to south.
Now: how are we to account for the fact that the river beds from west to east, irrespective of volume and velocity and therefore of their erosive powers, namely, in order the Brahmapootra, Mali-hka, ’Nmai-hka (western and eastern branches of the Irrawaddy re- spectively, the latter being the maz stream), Salween, Mekong, and Chin-sha (Yangtze), lie at successively higher and higher levels? The problem is complicated by the fact that the rivers are of different ages, the Irrawaddy evidently being the most recent, while the Chin-sha is probably the oldest. The regularity of the ascent is not due to a progressive decrease in the erosive power of the rivers, due either to.a decrease in grade, to a decreased volume of water, or to any difference in the composition of the rocks over which they flow. The Mekong is a bigger and swifter river than the ’Nmai-hka, but it flows:at a higher level by some 2,000 feet. The Salween has a bigger volume of water than the Mekong, but flows over 1,000 feet below it. We cannot ascribe the phenomenon to chance, and the only explanation seems to be that the country realty does represent an inclined block of strata; and unless it has itself been planed down and carved out in this way, which is what we are endeavouring to show that it has not, and that it never existed above water except as a series of parallel ridges and valleys, we are almost forced to the conclusion that it must have been pushed bodily up over an inclined plane of older rock which it now overlaps. This sorts well with the belief, founded on a consideration of glacial phenomena and floral distribution, that the ridges were pushed up one by one from the west, by a lateral movement of the Himalayan axis. If such bodily movement of the mass did take place, it is easy to account for the rifts in which the rivers now flow, by fracture. If the pressure which gave rise to the original underlying synclinal structure was sufficient also to force this huge mass bodily up an inclined plane of older strata, sloping gently down to the west, at less than a degree,*
1 If the slope from the Chin-sha Valley to the Brahmapootra were uniform, it would be, in round numbers, about 1 in 3,000, or a slope of 20 seconds.
=)
F. Kingdon Ward—The Land of Deep Corrosions. 215
then any cessation or diminution of that pressure might allow the overlaying strata to sag back. The result would be that on the steeper slopes—for the slope from west to east is manifestly not uniform—the massive anticlines, dragging on the synclines, would cause the latter to crack, and rifts such as the parallel rivers now occupy would take the place of simple anticlines, accounting at the same time for the differences of level at which the rivers flow. The rifts once formed would be deepened by erosion, the valley walls being protected by the aridity enjoyed, which is itself increased automatically by the up-valley winds. It is, however, evident that these aggravating factors alone are not sufficient to account for the rifts in the first instance, since the Salween, south of latitude 28° in a monsoon region, flows through a very narrow valley, the rocks in the bed of which in all respects resemble those further north, and in places through gorges modified by the heavy summer rainfall; still more does the upper ’Nmai-hka (or Taron as it is now called) flow in a gorge, though the region is drenched with rain almost all the year round,
Or, we may account for the rifts, and perhaps also for the marked differences of level, not by any lateral movement of the Himalayan axis, but by the elevation of that range itself, setting up a great tension strain at right angles in the adjacent crust, causing a sequence of parallel rifts to appear during the second phase referred to above, followed by an irruption of molten rock along the lines of weakness. - Lines of volcanic activity can be followed southwards from Batang through Yunnan (‘I‘engyueh volcano), Burma (Popa), the Arrakan Hills, and the Andamans (Barren Island), to the Indies, where the voleanic forces are at present concentrated, having forged southwards like a line of fire. In the case of a tension strain like that, the region most affected would be that nearest the seat of force, that is in the west nearest the Himalayas, where the broadest and deepest valleys would be formed; the least affected would be those furthest away, in the east, which would consequently be narrowest and highest. But while the rift formation may be due to this cause, and not to any pushing of the crust up a gently inclined plane with subsequent sagging back, it does not affect the synclinal origin of the great breach in the Sino-Himalayan axis, and the successive elevation of the parallel divides, the most easterly being those first elevated. This I now regard as proved from botanical and geological evidence.
It will be noticed that there is a tendency for the river valleys not only to lie at higher elevations, but also to become narrower, so far as is consistent with their different powers of erosion, as we go eastwards. Thus the Brahmapootra valley, once the Himalayan axis is cut across, is broader and flatter than that of the Mali, and the Mali than that of the ’Nmai-hka. There is probably little to choose between the gorges of the upper ’Nmai-hka (Taron), the Salween, and the Mekong, as regards breadth,’ but the Yangtze valley is rather broader, the river itself being quite twice as broad as the Mekong. If no disturbing factors intervene the western rivers will eventually tap the eastern, owing to the cutting back of the tributaries
216 F. Kingdon Ward—The Land of Deep Corrosions.
on the rainy sides of the several divides and the gradual shifting of the watersheds eastwards. This is inevitable. Thus the ’Nmai-hka will tap the Salween, and the Salween the Mekong, south of latitude 28° (the southern limit of the arid region on the former river). The Mali might tap the ’Nmai—the watershed hangs nght over the latter river at present, and the former will then become the main stream of the Irrawaddy, the ’Nmai disappearing; but an elevation of the Salween—Irrawaddy divide, by further concentrating the monsoon wind currents within the Irrawaddy basin, might prevent this by levelling up the present unequal distribution between the Mali and the ’Nmai; but it would also curtail tapping operations further east, south of the arid region, just as they have been stopped in the arid region itself, where the rivers grind out their gorges in isolated grandeur, indifferent to the freaks of their neighbours because independent of water save from the distant glaciers of Tibet.
It may be that the Mali has already tapped tributaries once flowing to the ’Nmai, and that it is gradually stealing all its waters on that side; certain it is that no rivers flow to the’ Nmai-hka from the west, and whereas we reached the crest of the Mali-’Nmai divide the second day after leaving the latter river, an endless series of ridges and valleys had to be crossed, occupying nine days, before the Mali was reached.
We come now to a brief description of the rocks in the valleys from the Yangtze to the Mali-hka, and on the intervening ranges in about latitude 28°. In the Yangtze valley slates and schists were noticed above, on the left bank, limestone below, but crossing to the right bank and ascending the Mekong—Yangtze divide the order was reversed—first schists, then limestone, after which came an outcrop of granite ; altitude 9,000-10,000 feet. All these rocks were highly tilted, sometimes almost vertical, the schists crumpled; dip varying, but approximating to N.E. The summit of the divide is capped by limestone and a red grit, probably arkose; the former sometimes cropping out in irregular cavernous bosses. Granite and schist also crop out in places, dip E.S8.E. at angles varying from 45° to 90°; altitude 15,000-17,000 feet.
Descending to Atuntsi we find chiefly mica-schists, and higher up limestones and slates. Atuntsi lies in a depression which is evidently a syncline. To the west rises a bulky outlier of the main divide, 15,600 feet above sea-level, composed chiefly of slates, with curious pillars of limestone cropping out on its east and west faces.
In the Mekong valley itself, purple and green slates are seen in the river bed, always standing on edge, and the same in the bed of the Salween ; the dip seems to decrease as one ascends. In a gorge of the Mekong just south of Atuntsi we pass from north to south through (1) vertical slates striking N.N.W., (2) granite, (3) lime- stone (?) ina few miles. Just south of the last is an outerop of coral limestone on the river bank. In the Mekong valley the schists and slates are everywhere almost vertical, the strike varying from N.N.E. to N.N.W. Altitude 7,000—9,000 feet.
At 10,000 feet on the Mekong—Salween divide the schists and slates met with were vertical, striking almost due south, giving a succession
F. Kingdon Ward—The Land of Deep Corrosions. 217
of narrow gullies on the main spurs, separated by razor-edged walls of rock standing out like ribs. The Mekong—Salween divide is here capped by granite, with outcrops of grey slate, instead of by limestone. Further north are various metamorphic rocks. Altitude 15,000— 17,000 feet. On the main spurs a succession of broken anticlines can sometimes be traced, causing the crests of the spurs, which are very steep-sided, to be jagged like a saw. Conglomerate was seen in one place at 17,000 feet.
In the valley of the Wi-ch‘u, which is crossed twice before the Salween is reached, limestone and schists, dipping north at high angles, are met with.
In the Salween valley the rocks are mostly limestone and granite in the north (i.e. north of Atuntsi), limestone, slates, and schists further south. The river cuts its way through remarkable gorges of granite and limestone, in some places crystalline, and at one place there are conspicuous scarps of the latter rock, like old river gorges, a thousand feet or so above the river.
The summit of the next range to the west, the Salween—lrrawaddy divide, I have not yet crossed in this latitude, though I have several times seen its snowy peaks; but a hundred miles further south the great bulk of itis granite, with conspicuous cliffs and peaks of limestone cropping out lower down on the Burma side, and the same vertical slates reappearing in the bed of the ’Nmai-hka at least as far north as latitude 27°; still further north it appears to flow, like the Salween, through granite gorges.
Leaving the ’Nmai valley and continuing westwards to Hkamti- Loong (latitude 27°), we pass from the igneous rocks of the great mountain ranges to laterite and clays as the plain is approached, and finally to sands and alluvium on the plain itself, overlying a hard conglomerate which contains rolled pebbles of many igneous rocks. The plain is divided by three conglomerate! terraces of varying breadth, rising one above the other from the river and trending in a more or jess north and south direction; they appear to be old river terraces, but their discussion is irrelevant here.
Southwards of Hkamti-Loong we find in sequence fia north to south the following: (1) Gravel interstratified with sand, often iron- stained and showing current bedding; in places converted into conglomerate by the “weight of superincumbent rock and the infiltra- tion of water carrying iron salts in solution. (This is well seen in a nulla, the ‘conglomerate nulla’, three marches south of Hkamti.) I will digress here for a moment to comment on these interstratified sands and gravels. One cannot look at the upper Mekong in summer, its red flood hurrying along sticks and branches, and at the same river in mid-winter, its shrunken waters blue as the Mediterranean, without perceiving that a river which is largely fed by glaciers and melting snow, or one which flows through a region with marked dry and rainy seasons, may lay down strata of two distinct ty pes. Summer and winter deposits may in such case be as sharply demarcated as the
? The conglomerate is not solid right through, but forms an irregular ‘ pan’ at varying depths.
218 F. Kingdon Wurd—The Land of Deep Corrosions. -
annual rings of summer and winter wood in a tree trunk, and may be put to the same use, namely, to determine how many years it has required to build a certain thickness. Summer layers would be characterized by greater thickness, coarser material, and plant debris, winter layers by sand and mud (glacier mud) without plant remains. In the case of a very big river flowing to the sea through a country the climate of which was not uniform, these results would be more or less vitiated owing to other causes, namely, (1) the creation of a reservoir of material at the mouth of the river, and (2) the effect of tides in sorting and delaying the deposition of material; moreover, the lower course of such a river is invariably sluggish and incapable of moving more than the finer materials of denudation. ‘Thus, even if the sediment was deposited as quickly as it arrived, no reserve accumulating, the uniformity of the material in suspension and the selective influence of the tides would effectually mask any classi- fication into summer and winter strata based on the appearances of the river in its upper course. Thus no such sequence would be detected in the case of such rivers as the Yangtze and Mekong, in spite of arguments founded on their appearance in the region of the parallel rivers, for these rivers are always muddy at their mouths, where there are’great reservoirs of silt. But in the case of a river, glacier- fed or otherwise, pouring into a big lake in the monsoon region, if the river is not too long, and especially if it derives much water from melting snow in the spring, seasonal deposits might be conspicuous, and it is to such seasonal deposits that I ascribe the interstratified sands, gravels, and leaf beds of the Hkamti basin. To continue the enumeration of strata passed between Hkamti-Loong and Myitkyna, we have, after the sands and gravels: (2) silver-grey (due to the presence of white mica flakes), buff, and reddish sands with rounded quartz pebbles; friable earths; argillaceous sandstones; blue clays, and grey claystones, with leaf beds and nodules of iron pyrites. The materials are coarser in the north, gravels, conglomerates, and sands, finer in the south, claystones and friable earths, showing that the rivers flowed into the lake from the north. The numerous native iron-mines in this region probably owe their origin to the accumula- tions of vegetable remains. South of the Hkamti plain these soft rocks have been thrown up into a series of ridges running parallel to the river and to one another, from 3,000 to 5,000 feet above sea-level, cut across by rivers flowing from the main divide (the Irrawaddy-— Brahmapootra divide, or further south, the Irrawaddy—Chinwind divide) in the west.
8. Crumpled mica-schists, produced from sandstones and giving rise to the same friable red earth (or clay) as is derived from the sandstones further north—in the bright sunlight this red earth is a burnt-ochre colour, and a beautiful feature of the scenery, where the dense jungle allows of its becoming visible; and bluish slates. The direction of dip varies between south and east, being generally about 8.E. or E.S.E., at angles varying from 30° to néarly 90°.
4. In the bed of the ’Mali-hka just above the confluence, dark grey slates with quartz veins, dipping east at nearly 90°. These slates probably underlie the lake series, and seem to be identical
Notices of Memoirs—Artesian Water in Manitoba. 219
with the slates in the beds of the Mekong and Salween further north (i.e. in the north-east) and the oldest rocks in this region. It will be readily recognized how complicated is the geology of this region and how difficult it will be to unravel, not only on account of the vast extent of country involved and the physical difficulties of travel, but also owing to the alterations and displace- ments of the strata consequent on the great irruptions of granite, which is found from the river-beds, 6,000 feet above sea-level, to the erests of the Mekong—Salween divide at 18,000 feet, and to the fact that the Burmese hinterland is covered with impenetrable jungle. Tosumup. Everything in the arrangement of the rocks throughout this region so far as I am acquainted with it, points to a synclinal structure, or more accurately fan structure, between the Brahmapootra and the Yangtze, induced by a pressure acting from west to east as the final phase of crust movement, which breached a continuous Sino-Himalayan axis, the result of a previous crust movement from south to north. The present hydrography of the region is due to a fusion of two sets of rivers which have become involved since the second phase of crust movement; the peculiar loops into which some of the rivers have been thrown must be ascribed partly to the buckling and twisting of vertical strata consequent on pressure acting at right angles to the dip, whereby rivers following the strike of the rocks have been thrown out of their course. Finally, there has been a rift formation in addition, due to a lateral tension strain, acting at right angles to the long axes of the synclines, or to a sagging of the anticlines with consequent rupture of the synclines. Complications have been introduced by the bursting through of enormous masses of eranite, which have tossed aside and altered the sedimentary rocks. The whole of this region must once have been under water like the Hkamti plain, but in the east subsequent alteration has gone so far that there are no clays and sandstones left, and the further east one goes the greater is the metamorphism and crumpling of the rocks. Possibly the pressure which gave rise to these mountain ranges is still acting from the west, and the white mountains which lift up their heads so proudly will grow yet higher and grander; but the fires which blasted this corner of Asia are drawn, the great lakes are drained. Only the restless rivers still pour through the terrific breach in the Asiatic divide to the hot south, to be followed through the rent they had torn not less impetuously by the hordes of hardy northmen who, six centuries before Christ, overran the plains of Indo-China.
NOTICES OF MEMOTRS.
Arresian WarTeR 1N Manrropa.’ By J. B. Tyrrex. OR many years, in fact almost ever since Winnipeg has been a city, it has depended for its water supply on wells sunk through the impervious layer of Boulder-clay which underlies the city, into a bed of porous limestone from which water rises in great abundance. From these wells the city has been able to obtain
1 From the Canadian Engineer, vol. xxvi, No. 15, p. 574, April 9, 1914.
220 Reviews—The Coals of South Wales.
a plentiful supply of water which, while containing a slight amount of mineral matter, is absolutely free from any hurtful bacteria, or from organic germs of any kind.
The porous limestone into which these wells are sunk, and from which the water rises, extends to the north and west beneath a layer of Boulder-clay, and rises to the surface in a number of places in the country between Lakes Winnipeg and Manitoba at elevations varying from about fifty to one hundred and fifty feet above the level of the prairie at Winnipeg. The rain falls on these bare rocky areas, as well as on the adjoining clay-covered country, but instead of flowing away in rills and streams, as it does on the clay-covered country, it at once sinks into the porous limestone and flows through this limestone southward and eastward until it finally reaches the surface either in the large springs north of Winnipeg or through the wells at the city of Winnipeg itself. The quantity that flows from these springs and wells is therefore largely limited to the amount of the rainfall on those portions of the surface where the porous limestone is uncovered. Where it is covered, as it is in many places, most of the water derived from the rain either stands in small lakes and evaporates from the surface, or drains off towards Lake Winnipeg or Lake Manitoba by the many streams which unwater the country.
The underlying porous limestone through which the water percolates on its way from the exposed areas north-west of Winnipeg to the wells in Winnipeg is a magnificent natural filter which is protected from contaminating influences throughout the populated parts of Manitoba by a thick covering of impervious Boulder-clay. No other city on the continent is provided by nature with such a filter, and no city could afford to duplicate it.
RAV LEw Ss. horney I.—Memorrs oF THE Grotoeicat SurvEY oF ENeLAND and WALES.
Tur Coats oF Sourn Wats, WITH SPECIAL REFERENCE TO ‘THE Origin and Disrripurion or AntHracireE. By AuBrey SrraHan, M.A., Sc.D., LL.D., F.R.S8., and W. Pottarp, M.A., D.Sc., F.1.C., assisted by E.G. Raptry. 2nded. 8vo; pp. 78, with 10 plates. 1915. Price ls. 6d. E. Stanford, Long Acre, or any agent for the sale of Ordnance Survey Maps.
WITH A MAP, reproduced from Plate IV by permission of the Controller
of H.M. Stationery Office.)
NOR a long series of years the energies of those geologists who are also chemists seem to have been so concentrated upon questions
of crystallization and the differentiation of igneous magmas that the corresponding and equally interesting problems of continuous variation in the composition of beds of sediment have remained outside the scope of their activities. To the nation sedimentary rocks are at least as important as igneous rocks. To our industries they are even of greater importance; and to those who have been called in to. help in mobilizing home resources of raw materials and providing manufacturers with efficient substitutes for sedimentary materials.
till lately imported in bulk from abroad, the failure to take stock of _
this whole class of the nation’s resources has seemed a neglect which
Reviews—The Coals of South Wales. 221
requires to be taken in hand at once. Among sedimentary rocks there is no class so essential to commerce as coal, and among coals there are none of greater national importance than are the anthracites of South Wales. It is therefore only to be expected that when we seek the best available account of the composition of beds of sediment and the lateral variation of those compositions from place to place, we should find it in a publication of H.M. Geological Survey which deals with the coals of South Wales.
Ever since the days of De la Beche and Playfair (1848) the steam coal of the Navy has been a subject for chemical specification and research ; but though analyses of coals from many localities have accumulated, the geological data concerning the samples were generally so little precise that until the present century the results of the analyses have hardly been dealt with by geologists and do not seem ever to have been employed to throw light upon the natural history of the rocks.
The Geological Survey Memoir on the Coals of South Wales was first published in 1908. Its main feature was the assembling of a great number of trustworthy and complete analyses of coals which had been collected, with proper precautions in sampling, from all the more important coal-seams, at localities which were distributed as widely as possible over the length, breadth, and thickness of the Coal-measures of the South Wales Coal-field. The analyses were all performed systematically, by standard methods, on samples collected by men whose business is not the buying or selling of the coal; and being all therefore strictly comparable with each other, they have proved of special value to those who are concerned with the commercial exploitation of the field. For the geologist, whose main concern is with the generalizations which emerge from the statistical treatment of these tabulated analyses, rather than with the figures themselves, it was the summarization of the analyses, each under the so-called “index of anthracitization”’ (a number obtained by dividing the percentage by weight of carbon by the percentage by weight of hydrogen contained in the coal), which marked the great advance.
Until the memoir appeared, the view that, in South Wales, anthra- citization of the coals was an event contemporaneous with the deposition of the measures, was only one among several alternative hypotheses. Now, however, as the result of the field and laboratory work set forth in the memoir, this hypothesis has advanced to the foremost place, and the diagram maps, which show the iso-anthracitic lines for each of the more important seams or groups of seams over the coal-field, form an excellent demonstration of the forcefulness of the evidence which supports it. Iso-anthracitic lines are obtained by plotting, on separate maps for each coal-seam, the index of anthra- citization for the samples of coal analysed, each at the geographical locality from which it was collected, and by drawing contour-lines among the ‘ spot-levels’ so obtained. In each of the seams or groups of seams for which they are illustrated, the iso-anthracitic lines have come out as sweeping sub-parallel curves, which range about axes or centres peculiar each to the particular seam or group of seams which
Reviews—The Coals of South Wales.
222
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-(GT61) “po pug ‘apoviyjup fo uoynquysig pun wbruig ay)
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Reviews—The Coals of South Wales. 223
is the subject of the illustration, which centres are situate in some eases within, in others beyond, the present northern boundary of the coal-fieid. (See Map on p. 222.)
Assembling the alternative hypotheses for the purpose of destructive criticism, Dr. Strahan notes that in taking the view ‘‘that the differences between anthracitic and bituminous coals in South Wales are mainly due to original differences of composition ’’? he was guided by four main considerations, the first three of which seem to be adequately proven by the diagrams given to show the distribution of iso-anthracitic lines. These four considerations may be summarized as follows: (1) ‘‘ Groups of seams possess a certain individuality,’’ and ‘‘in some there are local anthracitic areas of which no evidence appears in others . . . but bands of the same seam may show considerable differences of composition’. (2) ‘‘Iso-anthracitic lines show no definite connexion with the faults and disturbances,” and ‘‘ though the strata may be vertical or even inverted and sharply folded as in Gower, yet the coal-seams retain the composition proper to that part of the coal-field”. (3) ‘‘ Anthracitization is obviously not connected with the existing outlines of the coal-field as determined by denudation,” and ‘‘ there is no connexion between anthracitization and depth from the present surface”’.. (4) is based upon the con- sideration of the proportion of inorganic ash which remains when the coals are combusted. ‘‘The comparative freedom of anthracitic coals from ash” was ‘“‘ already brought out by Mushet’s analyses” as long ago as 1840, but it has remained for the present generation to discover that when a sufficient number of Welsh coal analyses are assembled the percentage of ash rises ‘‘ with fairly steady gradient from 1 per cent at the anthracitic end to more than 6 per cent near the bituminous end of the scale’’.
These four main considerations all point to an early date for the formation of the anthracite of South Wales, and if it be accepted that variation in the percentage of ash ‘‘ cannot be due to subsequent alteration” of the coal it must follow that anthracitization took place contemporaneously with the deposition of the Coal-measures.
A fifth line of evidence, based upon the finding of certain ‘‘ true pebbles” of coal (remanié from the breaking up of some already consolidated seam) among the sandstone pebbles which form the conglomeratic beds interstratified with the Pennant Grits of the Upper Middle Coal-measures, clinches the argument.
In the second edition of the memoir now before us the number of tabulated analyses has been increased to 821, which, with the inclusion of the results of direct determinations of the percentage of moisture and of the calorific value for forty-seven of the samples analysed, will make it by so much the more valuable to commercial men. The new samples have been collected during the recent revision of the maps of the coal-field, all under the standard conditions of sampling observed for those dealt with in the first edition. Of the 118 new analyses, some were done in the Survey laboratory and many by the staff of the Government laboratory : much credit is also due to Mr. C. A. Seyler, who, working first for and later in collaboration with the officers of the Geological Survey, has
224 Reviews—Mineral Resources of Great Brita.
been responsible for no less than 101 of the analyses now tabulated. So far as the geological conclusions are concerned, all the arguments put forward in the first edition are somewhat strengthened, and the net result of the revision is a greater precision in the location of the lines of iso-anthracitization in the charts for the various seams. In the letterpress we find additional comments by Dr. Pollard upon certain more modern methods of analysis introduced by American and other chemists since 1908, but for the sake of uniformity none of these has been adopted. In the last pages of the memoir Dr. Strahan allows himself to draw tentative conclusions concerning the physical geography in South Wales and Ireland in Carboniferous times, and we find it definitely suggested that it was some peculiarity of physical geography in South Wales and Ireland which led to the differentiation of the material in the coal-seams. ‘‘ As the coast-line retreated northward the area of anthracite coal shifted and kept pace with it,” and the rule ‘‘that each seam in any locality is less , anthracitic than its predecessors . . . is a necessary accompaniment of the formation of anthracite at successive intervals at a more or less constant distance from a retreating shore-line’’.
Of the labour involved in the preparation of the memoir only those who have personal experience of quantitative analysis of coal are competent to judge. The general laws governing the ‘‘ oradation into anthracite’? in South Wales have been made clear, and even allowing for the unique opportunities offered by a coal-field which is in course of active development over almost the whole of its extent, it may be fairly claimed that this is no small accomplishment, a result certainly to be accounted as of ‘‘ both scientific and economic value’’. What has been done for anthracite may be extended to other groups of sedimentary rocks, and if geologists who have adequate experience of the arts of chemistry, or chemists who have sympathy with the requirements of geology, can be persuaded to take up the work, further discoveries of equal scientific interest and of perhaps even greater advantage to the nation’s commerce should reward their efforts. To such workers we commend the second edition of the Survey memoir on the Coals of South Wales as a model worth following when they present their results. W. G. F.
IJ.—Tue Gronogican Survey on THE Mrnerat Resources oF Great Brrrary.
ee the stress of a protracted war it behoves belligerent countries to’
take careful stock of their resources. The special reports by the Geological’ Survey on the Mineral Resources of Great Britain, of which three volumes have appeared—the first (pp. 59, 1s.) on Tungsten and Manganese Ores, the second (pp. 93, 1s. 6d.) on Barytes and Witherite, and the third (pp. 57, 1s.) on Gypsum and Anhydrite—are timely and very welcome. Some legitimate surprise may perhaps be felt that such obviously useful publications had not been issued long ago, before the cloud of war loomed and broke, but in this country the State was ever chary of assisting and stimulating industry, and the Geological Survey constitutes no exception to the general rule of Government departments. It is remarkable that for
Reviews—Lower Paleozoic Fossils of Burma. 225
many substances of vital importance either for or in connexion with the production of munitions of war we should have allowed ourselves to be entirely dependent on foreign sources. Tungsten is a case in - point. Practically all the ore is produced in the British Empire, yet it was all shipped to Germany and worked up there. The country is, however, now awake to the danger of allowing key industries to be entirely in hands which might become hostile. Another urgent reason for making the most of resources actually in the country is the necessity for restricting our imports as much as possible. Intelligent prospecting might bring to light mineral ores from which might be produced many chemical substances at present imported and fast growing scarce.
All the volumes follow very similar lines. The chemical composi- tion and physical properties of the minerals supplying the substances in question are described very briefly; this section might with advantage have been expanded so as to make the identification of the minerals easier for those not skilled in the subject. A section follows on the commercial uses, with statistics, and the method of treatment. The mode of occurrence is then discussed, and -the principal mines are described in some detail. The list of localities is not exhaustive: possibly none were included which were not repre- sented by specimens in the Museum in Jermyn Street.
Of the substances dealt with, tungsten and manganese are largely used for alloying steel, the former having also an extensive use for the filaments of incandescent electric lamps; barytes is required in the preparation of white paints and for wall-papers, while witherite is the principal source of barium compounds; gypsum furnishes the familiar plaster of paris, and celestine and strontianite are the sources of the strontium used in sugar refining.
Il1.—Lowerr Patmozorc Fosstts or Burma.
SuerpLeMENTARY Mermork on NEW OrDovicIaAN AND Siturran Fossixs FRoM THE NortHEerN Swan States. By F. R. Cowper Reep. Paleontologia Indica, n.s., vol. vi, Mem. 1, viii + 98 pp., 12 pls., 1915.
(Y\HE memoir to which this is supplementary was published in
December, 1906, under the title The Lower Palgozoice Fossils of the Northern Shan States, Burma, by F. R. C. Reed, with a Section on Ordovician Cystidea, by F. A. Bather. In that memoir fossils were described from the Naungkangyi and Nyaungbau Beds of the
Ordovician, and from the Namhsim and Zebingyi Beds of the Silurian.
From those beds further fossils are now described, but the chief
interest lies in those from two fresh sets of beds which are, on their
evidence, referred to Lower Silurian and Middle Ordovician.
_ The stratigraphical succession, from above downwards, is as
follows. Sizurran: Zebingyi Stage, transitional to Devonian ;
Namhsim Stage, consisting of the Upper or Kénghsa Marls, with
Phacops shanensis, correlated with Lower Ludlow, and the Lower
or Namhsim Sandstones, with Phacops longicaudatus, var. orrentalis
and Lllenus namhsimensis, n.sp., correlated with Wenlockian; and the DECADE VI.—VOL. III.—NO. V. 15
226 Reviews—Lower Palwozoic Fossils of Burma.
Panghsa-pye Stage, consisting of an Upper or Graptolite Band and a Lower or Trilobite Band (to these we shall recur). Onpovicran : Nyaungbaw Limestones with ‘‘Camarocrinus asiaticus” ; the Upper Naungkangyi Beds, comprising the Hwe Maung Purple Shales; the Lower Naungkangyi Beds, with the rich Cystid fauna of Sedaw, probably Llandeilian ; and the Ngwetaung Sandstones with a species of Orthis.
The rocks of the new Panghsa-pye Stage are of interest, not merely from their richness in organic remains, but from the occurrence of graptolites in the upper beds. These, as determined by Dr. Gertrude Elles, indicate three horizons, two of Lower Llandovery age, and the third suggestive of the Wenlock Shale. From the lower Trilobite Band are recorded some plates assigned to Zurrilepas, but, since no figures are given, it is impossible to decide whether this reference would be correct according to more recent views.
The Upper Naungkangyi Beds, of which the Purple Shales may be a local facies, are exceedingly fossiliferous and have yielded many new species. The trilobites on the whole indicate an horizon corresponding with Stage C of the Baltic Provinces, and Ashgillian types do not appear. In both sets of beds there occurs a new lamellibranch of the Family Vlastide, which Dr. Reed names Shanina vlastoides. The trilobite Pliomera ingsangensis Reed, has also been found in both facies, and is now made the type of a new subgenus Lncrinurella. Of this subgenus no definite diagnosis is given, but the main diagnostic characters appear to reside in the glabella, which resembles that of Hnerinurus. On p. 97 Dr. Reed notices ‘‘the absence of cystideans”’ from the Hwe Maung Purple Shales; but Mr. T. H. D. La Touche, to whom the distinction of these beds is due, said: ‘‘ the more argillaceous portions of the rock are highly fossiliferous, containing large casts of fragments of crinoid stems, cystidean plates, etc.” (Mem. Geol. Surv. India, xxxix, part 2, p. 92, 1913).
Reference to Mr. La Touche reminds us that in the same paper (p. 65) he stated definitely, what those familiar with the literature had already assumed, namely that Camarocrinus asvaticus Reed, was identical with Lchinospherites kingi Noetling (see Guot. Mae., 1892, p- 521). The reference of Camarocrinus to Scyphocrinus was also made clear at least as early as 1907. From this it would appear that Camarocrinus asiaticus should be known as Seyphocrinus kingt. It is, however, very doubtful whether Noetling’s name can be accepted, so that we may perhaps correctly speak of Scyphocrinus asiaticus.
Dr. Cowper Reed is to be congratulated on the enthusiastic industry with which he tackles these large and varied collections of fossils. ‘The same congratulations can hardly be extended to his would-be readers. It may be that, in the present case, the War has increased the natural difficulty of correcting proofs from a printer in Caleutta; but mis- spellings and misplaced commas are minor evils. What is to be deprecated seriously is the impression conveyed by so many of these large memoirs, that they are notes jotted down currente calamo and sent to the press without further revision. From too many sentences the author’s meaning can only be extracted by a prolonged process of
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Reviews—Dutch Pliocene Fauna and Flora. 227
interpretation. Till Dr. Reed shows more respect for his public, his erudition, energy, and ability will not receive the recognition that is their due.
1V.—Tae Puriocene Froras or tran Dorcu—Prusstan Borper. By Crirment Rep, F.R.S., and Exeanor M. Rem, B.Sc. Mededeelingen van de Rijksopsporing van Delfstoffen, No. 6. pp. 180, with 4 text-figures and 20 photographic plates. ’s Gravenhage: M. Nijhoff. 1915. Price fr. 16.50.
R. AND MRS. REID have developed on lines of their own the study of the fossil fruits and seeds of the Tertiary floras. They have worked for many years on the Pleistocene and Pliocene deposits ot Britain ‘‘in the hope of obtaining some approximate measure of geological time, some idea of the succession of climatic changes, and some insight into the origins and migrations of successive faunas and floras”. Asa result of their work we have become acquainted with a sequence of small floras working backwards from the comparatively modern Roman deposits through Celtic, Neolithic, Glacial, Inter- glacial, and early Glacial strata to the latest Pliocene stage repre- sented in the Cromer Forest-bed. But as in Britain there is here a break in the succession, the earlier Pliocene deposits being marine and containing no plants, the authors have been forced to look abroad for the continuation of the history of the Pliocene flora of North- Western Europe, and hence have undertaken the examination of the Phocene flora which has been recently discovered at Limburg on the Dutch—Prussian border. In view of the remarkable results obtained from the study of the Upper Plocene flora of Tegelen, which were published in 1907, the publication of the detailed account of Mr. and Mrs. Reid’s further work in the same region has been awaited with much interest. ‘The Reuverian flora, as the authors style it, from the name of the principal locality, is found to be of an older type than the Tegelian, ' though many plants are common to the two. It indicates a warmer climate, and is classed as Middle Pliocene. Up to the present nearly 300 species have been examined; of these the authors have been able to suggest the botanical position of about 230 ‘‘ with some degree of certainty’, and of a lesser number ‘‘ with considerable certainty.’’. The results arrived at are of great interest. ‘The trees and shrubs, which form the most peculiar and striking element in the flora, show a close relationship with the mountain flora of Western China at the ‘present day. Thus, among the species found in Limburg are Gnetum scandens, Magnolia Kobus, Zelkowa Keakt, and other present-day Chinese species. Others occur which, belonging to genera now extinct in Kurope, are still represented in China by closely allied species; such is Meliosma europea, closely allied to IL, Veitchiorum of the mountains between China and Tibet. Again, when the genus in question is common to both Europe and China, it is often a Chinese or Japanese species that most resembles the Reuverian plant. The Reuverian flora suggests a mean temperature similar. to that of Southern France to-day, but the Chinese alliance is more strongly
228 Reviews—Geology of Western Australia.
marked than that with the existing flora of the Mediterranean area. The flora as a whole was probably much richer in species than the present-day Central European flora, and was possibly comparable in variety, in the number of its species, and in the abundance of its trees and shrubs with the present-day flora of Western China.
Coming to general considerations of plant-distribution, the authors, developing the now well-known resemblance between the Eastern North American and East Asiatic floras, conclude that the Reuverian fossils indicate one of three great streams of migration southwards from a common centre in the north, the other two being the Chinese and North American. The two latter found an open route to warmer regions and survived; the Reuverian, on the other hand, found a barrier of seas, deserts, and mountains and perished under the rigorous climatic conditions before which it was retreating.
The greater part of the volume is occupied with a detailed systematic description of the fruits and seeds which have been separated from the lignitic material. Some botanists may find points of issue with Mr. and Mrs. Reid in their general conclusions or in some of their specific determinations, but all must admire the wonderful patience, industry, and skill of which the present work is a monument. The hundreds of beautiful photographic reproductions of the objects described are alone of inestimable value. We hope that the authors will be able to continue their exploration of these interesting deposits.
AC Beans.
V.—GerotocicaL SurvEY oF WerstERN AUSTRALIA.
ULLETIN No. 61, An Outline of the Phystographical Geology (Phystography) of Western Australia, by J. T. Jutson, is a deliberately educational volume designed to aid the citizens of the State to a juster appreciation and a greater knowledge of the land in which they dwell. The treatment throughout is thoroughly modern, and owes much to the American school of geographers headed by W. M. Davis. West Australia is a country of extreme geological antiquity, and its great interior plateau, formerly a peneplane, is now in a cycle of desert erosion. It presents a series of unique physiographical problems, of which, notwithstanding the present work, only the fringes have been touched. Mr. Jutson has produced a work of extreme interest, readable throughout, which will certainly form the starting-point for all future investigation of this subject in Western Australia.
Bulletin No. 56, Zhe Geology of the Country between Kalgoorlie and Coolgardie, by C.S. Honman, serves as a connecting lnk between previous bulletins describing the country around the above-mentioned mining centres. The rocks consist of a series of inclined and folded metamorphosed sedimentary rocks, probably Pre-Cambrian in age, with intercalated beds regarded as volcanic rocks. The whole series is invaded by basic and acid intrusive rocks, but, unlike the neighbouring areas, it contains few ore-deposits. The scale on which geological surveys are carried out in our great Dominions
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Reviews—Professor Bonney—On certain Channels. 229
is exemplified in Bulletin 57, A Geological Reconnaissance of a portion of the Murchison Goldfield, by H. P. Woodward. We are told that the area dealt with embraced 3,300 square miles, and that the work was carried out chiefly in 1912 with some unavoidable interruption. The country consists chiefly of granite, with ancient crystalline schists, and shows wonderful examples of arid erosion, many of which are figured. The bulletin contains an account of the economic geology of the area, including two tin fields, an occurrence of emeralds, and aboriginal ochre mining. The emeralds are derived from pegmatite veins cutting mica-schists, and the occurrence is of value as the gem is now very scarce.
Bulletin No. 59 is a collection of Miscellaneous Reports containing eighteen short papers, mostly preliminary observations on various ore-bearing areas of the State, issued in this form so as to ensure prompt publication of the valuable mining information they contain. Gold is, of course, the main quest; but occurrences of tin, lead, copper, coal, and rare metals are also dealt with in this bulletin. There are also two petrological papers, and one on Western Australian meteorites.
Cowan:
VI.—Ow cerrain CHANNELS ATTRIBUTED 10 OVERFLOW STREAMS FROM Icz-pammep Laxrs. By Professor T. G. Bonnny, F.R.S. pp. 44. Cambridge: Bowes & Bowes. 1915. Price 1s.
LTHOUGH Professor Kendall’s explanation of the so-called overflow channels of the Cleveland district has been applied to similar phenomena in East Lothian, Cumberland, Dublin, and elsewhere, a number of objections of a general character have been raised from time to time. In the Presidential Address to the British Association in 1910 Professor Bonney stated the difficulties involved in the “‘land-ice theory’, and in the pamphlet under review these difficulties are reiterated and the result of a detailed examination of several of the above-mentioned localities discussed. Although at the present day marginal lakes are uncommon, most of the Alpine examples being small and possessing no overflow channels, certain criteria such as beaches, deltas, floor-deposits, and overflow channels are considered to be indicative of the former presence of such lakes. In the case of Glen Roy the evidence consists mainly of the first two, but in the North of England the last is the only significant criterion. Professor Bonney holds that the ‘railway cutting’ trenches must have been cut by mature rivers, and that their form is not such as would be expected from lake overflows, even where the latter would carry much debris. He prefers to consider them as the ‘‘ relics of ancient, sometimes very ancient, valley systems and not such modern features as the glacial theory demands”. Various facts seem to favour this hypothesis: for example, the channels sometimes occur in an aligned series, while they are often cut by later transverse streams. Again, overflows would tend to be spasmodic, while the resultant trenches would, like Alpine sub-glacial streams, tend to be V-shaped. The absence of deltas seems significant, since overflow streams would
230 Reviews—Ore Deposits, Alaska Peninsula.
be heavily charged with debris; Thoroddsen has recently described the blocking-up of fiords in Iceland by the debris carried by jokull-vatn.
The glacial theory of the in-and-out channels is also unsatisfactory. In the case of a stream flowing between a glacier and a hillside it is very probable that the latter would be much more resistant than the former, so that the stream would tend to cut its way into the ice and to lower the level of its bed. Thus, instead of a flat ‘bench’ along the hillside, the latter would be in the form of a shelving slope working gradually towards lower ground. Professor Bonney offers two alternative explanations: one that the ‘out’ portions are the remnants of. valleys, one wall of which has been worn away by marine erosion ; the other, that one bank has been greatly steepened by warping subsequent to the formation of the channels.
The widespread occurrence of these dry valleys and the variety in form render it probable that no single explanation satisfies all the examples. Some must be assumed, at present, to be due to ‘overflows’, as it is impossible to correlate them with any former drainage systems; others, such as the large cross-cut near Cader Idris, strongly favour the view that such channels may originate without the assistance of glacier lakes. It also seems possible that some may arise by the re-excavation or clearing out of older filled-up valleys by the action of glacial streams. This would explain why these pre-glacial valleys are free of glacial material and at the same time satisfy the glacialists who maintain that the form of the trenches is that which would be expected from the action of heavily laden streams with comparatively low gradients.
A. 8S.
VII.—Gerotogy anp Ore Depostrs or Copprr Mountain anp Kasaan Prninsora, Atasxa. By C. W. Wricur. U.S. Geol. Sury. Prof. Paper No. 87, 1915. pp. 110, with 22 maps and plates.
({\HE Prince of Wales Island, the largest of the southern islands of
Alaska, is separated from the mainland by Clarence Strait, which with its numerous branches breaks South-Eastern Alaska. into numerous islands and peninsulas. The network of fiords extends northward from the Portland Canal. The country shows abundant signs of glaciation, but has no existing glaciers, and owing to its
mild moist climate, its latitude of only 55° to 56°, and its long summer
days, it is covered with a vegetation which, though mainly coniferous,
is often as dense as tropical jungle. These forests have greatly hampered the geological survey of the area, which has been stimulated by its valuable copper deposits. The survey by Messrs. F. E. and
C. W. Wright shows that the country has an Archean foundation, on
which rest Silurian, Devonian, and Carboniferous sediments. During
Lower Mesozoic times it was intruded by a great series of plutonic
rocks, and extensive andesitic lavas were discharged on the surface.
As usual in Alaska, the chief Kainozoic formation is a great series of
continental sediments of Eocene age; they were followed by basaltic
eruptions, some of which have taken place in post-Glacial times.
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Reviews—Tertiary Mollusca, New Zealand. 231
The complex of fiord channels and valleys is shown by the geological maps, especially by that of the Kasaan Peninsula, to be quite independent of the older grain of the country; the arrangement of the fiords is inexplicable on any theory of glacial erosion, and is only explicable by their origin along intersecting Upper Kainozoic fractures. The ore deposits are numerous bodies of copper ores in the contact zone, where granite has been intruded into limestones. The - ores occur in shoots, which though near the contact are not exactly along it. ‘The memoir is a valuable addition to the economic geology of Alaska.
VIII.—Revision or tar Tertiary Motiusca or New ZrALaND, BASED on Type Marertat. By H. Sorer. New Zealand Geol. Surv. Pal. Bul. No. 3, pt. ii, 1915. pp. vii, 69, with 9 plates.
\ R. HENRY SUTER, the consulting paleontologist to the il Geological Survey of New Zealand, has completed his useful redescription of a series of types of New Zealand Kainozoic Mollusca of species founded by Hutton, Mr. EK. de C. Clarke, Dr. J. A. Thomson, and Professor Marshall. He has established one of McCoy’s list Names as a new sub-species. ‘The revision is illustrated by nine excellent plates. The species range from the Miocene to the Pleistocene; the majority are Pliocene. Mr. Suter accepts the Oamaru Beds as Miocene, which is consistent with the conclusicns of McCoy and Chapman as to the age of the corresponding fauna in South-Eastern Australia. On p. 37 he, however, leaves the Australian range of Bathytoma haasti as Kocene, whereas from the localities cited it would also be more correctly included in the Miocene.
IX.—Tue Inorcanic Constituents or Ecarnoperms: By F. W. Crarke and W. C. Wueeter. U.S. Geol. Surv. Prof. Paper No. 90L, 1915, pp. 191-6.
ESSRS. CLARKE AND WHEELER have extended their interesting researches on the composition of the Crinoid skeleton to the KEchinoids and Stelleroids. ‘hey find by nine analyses of Echinoid plates that the amount of carbonate of magnesium in the shell ranges from 6 to 134 per cent, and that the geographical distribution of the specimens shows that the proportion of magnesia is inversely to the latitude. A series of analyses of the joints of the Starfish and Ophiuroids shows the same conclusion ; the proportion of magnesium carbonate ranges from 7:79 to over 14 per cent, and as a rule the proportion is highest in specimens from the warmest seas. A limestone therefore formed of the remains of Echinoderms which had grown in a warm sea would give rise to a magnesian limestone. The authors announce their intention of extending their investigation to other marine invertebrates to determine whether their skeletons show the same distribution of magnesia, so that magnesium sediments would naturally be deposited more in warm than in cold climates.
232 | Brief Notices.
X.—Brier Norticrs.
1. East Loruran. By T.S. Murr. Cambridge County Handbooks. pp. 177. 1915. Price 1s. 6d. net. ; HIS useful little volume maintains the high standard of the now familiar series to which it belongs. The county includes parts of the Central Plain and of the Southern Uplands, and boasts a picturesque coast, thus affording scope for a highly interesting geographical study.
2. Vicror1an Tritopites.—In his series ‘‘ New or little-known Victorian Fossils in the National Museum”, Mr. F. Chapman has recently published a description of some Trilobites from the Yeringian (Upper Silurian) beds. These include new species of Goldius, Cyphaspis, and Calymene. Other genera represented are Proétus, Cheirurus, and Phacops. In adopting De Koninck’s name Goldius, 1841, in place of Goldfuss’ Bronteus, 1843 [not 1834], Mr. Chapman might have given a reference to the original publication. Life-size photographs of the specimens are reproduced, and when these fail in clearness an enlarged drawing is added—a very good plan.
3. HQuimseTITES IN JuRAssIc SHALE, WontHacel, Vicrorra.— Under the name Lguisetites wonthaggiensis Mr. F. Chapman describes the tuberous underground shoot of an equisetalean found in Jurassic shale from a boring at Wonthaggi, Victoria. Though Zquisetites has previously been described from South Gippsland, this is the first record of this particular structure from Australia (Rec. Geol. Surv. Victoria, vol. ili, p. 317).
4. Tue Ort anp Gas Fretps or Onrarto aND QueEBec. By Wryarr Matcoum. Canada, Department of Mines, Geological Survey, Memoir 81, No. 67 Geological Series, Ottawa, 1915. pp.i11+248.
N this memoir the author sets forth concisely the geological conditions existing in the southern parts of Ontario and Quebec underlain by sediments which have suffered little disturbance. The most important oil- and gas-producing fields lie in South-Western
Ontario. The oil pools of Oil Springs and Petrolia, opened fifty
years ago, occur in the Onondaga (Coniferous) formation, but gas and
oil have been found in the Salina (Onondaga), Guelph, Clinton, and
Medina formations. There has recently been a rapid decline in the
production of oil in spite of the discovery of new pools, but the gas
production has increased rapidly.
5. Coat Fretps anp Coat Resources or Canapa. By D. B. Dowxine. Canada, Department of Mines, Geological Survey, Memoir 59, No. 55 Geological Series. pp. vili+174. Ottawa, 1915.
fJ\HIS memoir is reprinted with some additions from the report on
the Coal Resources of the World presented to the Twelfth
International Geological Congress. Canada appears to have large
reserves of coal, but much of it is not available for the commerce of
the British Empire. Large supplies of bituminous and sub-bituminous coals exist in the western interior, and to a lesser extent on both
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Brief Notices. 233
coasts. The fields in Manitoba and Southern Saskatchewan supply lignitic coal well adapted for domestic use. The extensive coal- fields of Alberta, containing coals of a wide range of character, form Canada’s greatest coal reserve. The interior of British Columbia contains many coal areas.
6. Tue Position oF THE VIBRATION PLANE OF THE PoLARISER IN THE PxrrograpHic Microscopr. By F. E. Wricar. Journ. Washing- ton Acad. Sci., v, pp. 641-4, 1915.
N petrographic microscopes with fixed polarizers the plane of the transmitted light is parallel to either the vertical or the horizontal spider-line of the eye-piece. The better position is that in which most light is transmitted. The light from the sky is always partially polarized, the amount varying with the distance from the sun’s position, and further effect is produced by the reflection at the sub- stage mirror. ‘he second factor was found to be negligible. The first, however, is important, and to obtain the best illumination the observer should set the plane of the polarizer parallel to the vertical spider-line in the early morning and late afternoon, and at right angles thereto at midday, but, since the intensity at midday is so much greater than when the sun is low, the better position for a fixed polarizer is for the plane to be parallel to the vertical spider-line of the eye-piece.
7. A Surprz Device ror tat GrapuicaL SoLvrion oF THE Equation A=8.C: a Guotoeicat Prorracror. By F. E. Wricur. Journ. Washington Acad. Sci., vi, pp. 1-7, 1916.
Y the use of reciprocals the variables may always be taken as less
than unity. Rectangular co-ordinates, together with an arm revolving about the origin, are used in conjunction with squared paper, the scales being varied to suit the particular equation. The geological protractor is a particular form: from it the apparent dip of a bed can be read off directly for any angle of dip of stratum and for any azimuth of vertical section.
8. THe CorreLation oF Porasstum AnD Maenestum, Soprum anv Iron, In lenxous Rocks. By Henry S. Wasnineton. Proc. Nat. Acad. Sci., i, pp. 574-8, 1915.
fJVHE correlation of the elements has not yet received much study
except the relation based upon silicity. It appears that in igneous magmas potassium and magnesium, and sodium and iron, tend to vary together, the evidence being of two kinds—petrological and mineralogical.
9. PREssuRE as A Factor in THE Formation oF Rocks anp MINERALS. By Joun Jounstoy. Journal of Geology, xxiii, pp. 730-47, 1915.
ENERALLY the so-called physical changes (e.g. the melting- point of a pure substance) has been overestimated as compared
with the influence of pressure on chemical changes. Change of effective pressure will in general alter the configuration of the various fields of stability in a system, but the effect will not be marked unless the concentration of one of the components changes appreciably with the change of pressure. In any discussion of the
234 Reports & Proceedings—Geological Society of London.
course of crystallization from a complex magmatic system the mode in which the effective pressure varies must be considered as well as the mode of cooling, for change of pressure may affect the order of erystallization.
REPORTS AND PROCHEHDINGS.
I.—Grotocicat Socrery or Lonpon.
1. February 23, 1916.—Dr. Alfred Harker, F.R.S., President, in the Chair.
The following communication was read :—
‘‘On the Origin of some River-Gorges in Cornwall and Devon.” By Henry Dewey, F.G.S. (Communicated by permission of the Director of H.M. Geological Survey.)
In North Cornwall, near Tintagel, there is an area of peculiar topography characterized by the presence of an upland plain or plateau. The plateau is dissected by deep gorges, with their walls scarred by potholes through which the rivers flow in a series of waterfalls, cascades, and rapids. aux
This plateau is terminated inland by degraded cliffs rising abruptly from 400 feet above sea-level, while the plain slopes gently to the recent sea-cliffs, mostly over 300 feet high. The plateau has been cut across rocks of different degrees of hardness, and is overlain by deposits of detritus and peat. Wherever the plain occurs the scenery is featureless, and the land boggy and waterlogged.
The widespread occurrence of this plain over Cornwall and Devon at a uniform height suggests that in its final stages it was a plain of marine erosion. ‘he author accepts Mr. Clement Reid’s conclusion that its date is not later than Pliocene. Its uplift in post-Plocene times led to rejuvenescence of the rivers, initiation of coastal cascades, and the production of gorges aided by the formation of potholes.
At Lydford, on the western flank of Dartmoor, the uplift led to the diversion of the Lyd by a stream that breached the valley-side and tapped the head-waters of the river.
A small stream, the Burn, now flows past Was Tor and Brentor, through the valley formerly occupied by the Lyd. The shortened journey to the lowlands bestowed such enhanced cutting-power upon the river that it quickly incised a chasm through which it now flows more than 200 feet below the base of its former valley; while a tributary enters as a waterfall from a hanging valley near Lydford Junction.
The elevation of the land also led to formation of gorges of similar character in other upland plateaux. These plateaux have been described by Mr. Barrow in the Quarterly Journal of the Geological Society, and reference is made to them by the author in connexion with the effects upon them of the uplift.
There are thus in Cornwall and Devon two characteristic types of scenery, to which in great part these counties owe their charm. Wide featureless plains covered with heath and marshland and dominated by tors and crags, on which the drainage is sluggish and vague,
a
Reports & Proceedings—Geological Society of London. 235
alternate with deeply incised rocky ravines where rivers flow as rapids and cascades. These two types mark successive periods of erosion. Post-Pliocene uplift gave such increased cutting-power to the rivers that they quickly incised chasms in their former valleys, employing while so doing the activity of waterfalls and rapids.
2. March 8,1916.—Dr. Alfred Harker, F.R.S., President, in the Chair.
The President referred with regret to the death, on March 3, of Professor John Wesley Judd, C.B., LL.D., F.R.S., Past President of the Society. He spoke of the value of Professor
Judd’s contributions to geological science, and of his eminence as a teacher of the science, and stated that the Society was well represented at the funeral.
Dr. Aubrey Strahan, F.R.S., Director of H.M. Geological Survey, exhibited and described briefly a set of specimens from the Western Front, illustrating the character of the rocks in which trenches, tunnels, etce., are being dug. They included specimens from the Cretaceous and Tertiary formations showing remarkable similarity in characters to the contemporaneous formations in Britain.
The following communication was read :—
‘¢ Fossil Insects‘ from the British Coal-measures.’”” By Herbert Bolton, M.Sc., F.R.S.E., F.G.S., Reader in Paleontology in the University of Bristol.
The author describes six insect wings found in the Coal-measures of Northumberland, Lancashire, and South Wales. Three of these have been previously named, but not described in detail; the remaining three are new to science.
Atdwophasina anglica, Scudder, has been examined in detail, and is now regarded as a primitive type of the Proto- Orthoptera, in contradistinction to Scudder’s view that it is a Protophasmid, and to that of Handlirsch, who had removed it to a group of unplaced Paleeodictyoptera.
Paleodictyopteron higginsi is shown to be related to the Dictyoneuride.
A new genus and species is created for, a finely preserved Wing, intermediate in character between the Dictyoneura and Lnthomantis.
Among the varied fauna obtained from ironstone nodules in the Middle Coal-measures at Sparth Bottoms, Rochdale (Lancashire), is a basal fragment of a wing recognized as a new species of Sprlaptera, and this is now described.
An unusual type of wing from the Northumberland Coal-field is very suggestive of the Protodonata, and is described as a KID a tive of a new genus and species.
The author. also discusses the Proto-Orthopterous affinities of Pseudofouquea cambrensis (Allen).
236 Reports & Proceedings—Geological Society of London. —
3. March 22, 1916.—Dr. Alfred Harker, F.R.S., President, in the Chair.
Dr. A. Smith Woodward, F.R.S., V.P.G.8., exhibited specimens of the problematical ichthyolite, Celorhynchus, trom an Eocene deposit in the Ombialla district, Southern Nigeria, and discussed the nature of this fossil. Microscope sections of the well-preserved Nigerian specimens confirmed W. C. Williamson’s determination that Celo- rhynchus is an essentially dermal structure. A similar section of part of the rostrum of the teleostean fish Blochius, from the Upper Kocene of Monte Bolea, near Verona, showed an almost identical structure. The precise nature of this rostrum remained to be deter- mined, but there could be no doubt that the so-called Celorhynehus is the corresponding part either of Blochius or of an allied genus.
The following communication was read :-—
‘‘The Pseudo-Tachylyte of Parijs (Orange Free State) and its Relation to ‘ Trap-Shotten Gneiss’ and ‘Flinty Crush-Rock’.” By S. James Shand, D.Sc., F.G.S., Professor of Geology in the Victoria College, Stellenbosch (S.A.).
The rocks which are here described as ‘ pseudo-tachylyte’ occur in irregular veins in the granite-gneiss of Parijs (O.F.S.) ; they formed the subject of a communication to the Society on November 18, 1914, which has since been withdrawn. The author first regarded them as igneous intrusions ; in the account now presented he compares and contrasts these rocks with the ‘ trap-shotten gneiss’ of India and with ‘flinty crush-rocks’ from Scotland, Argentina, and Namaqualand. The veins are utterly irregular in form, dip, and strike; they freel branch and anastomose, but not uncommonly terminate blindly. The material consists of a very dense black base, holding numerous rounded and subangular fragments of granite; these are sometimes
so numerous that the base is reduced to the role of a mere cement
between the rounded boulders. With regard to their microscopic characters, the rocks fall into three types, one of which is very opaque and almost without individualized grains or crystals, while the others represent different stages of crystallization of the first type. It is shown that the production of the veins involved a temperature sufficient to melt the felspar of the granite, and that there has been extensive recrystallization of felspar in the form of spherulites and microlites, and also of prisms of hornblende. In this evidence of very high temperature, and in the entire absence of shearing phenomena in the granite, the pseudo-tachylyte of Parijs ditfers from all known crush-rocks and has affinities rather with pitchstones and tachylytes. Among the crush-rocks of Scotland, however, the author (following Clough, Maufe, and Bailey) recognizes a passage from the clearly mylonitic type to a type in which fusion has been practically realized; the latter material is closely similar to the first of the Parijs types. A chemical analysis of the psendo- tachylyte shows that the total composition is practically that of a granodiorite, and is such as might correspond to an average of the very variable dark gneiss in which the veins occur.
It is suggested that a ‘melt’ of granite, produced by mechanically developed heat arising from the sudden rupture of the granite, would
Reports & Proceedings—Geological Society of London. 237
differ in certain respects from a normal magma of granitic composition, and it is thought most likely that the veins represent the solid equivalents of such a melt.
4. April 5, 1916.—Dr. Alfred Harker, F.R.S., President, in the Chair.
The President announced that the Council had awarded the proceeds of the Daniel Pidgeon Fund for the present year to John Kaye Charlesworth, M.Sc., Ph.D., F.G.8., who proposes to conduct researches in connexion with the Glaciation of Donegal.
The following communication was read :—
“The Picrite-Teschenite Sill of Lugar (Ayrshire) and its Differ- entiation.””. By George Walter Tyrrell, A.R.C.Sc., F.G.S.
This sill occurs near the village of Lugar in East Central Ayrshire, and is magnificently exposed in the gorges of the Bellow and Glenmuir Waters, just above the confluence of these streams to form the Lugar Water. It has a thickness estimated at 140 feet, and is intrusive into sandstones of the ‘ Millstone Grit’. The contacts consist of a curiousiy streaked and contorted basaltic rock, passing at both margins into teschenite. The upper teschenite, however, becomes richer in analcite downwards, and ends abruptly at a sharp junction with fine-grained theralite. The lower teschenite becomes somewhat richer in olivine upwards, but passes rapidly into horn- blende-peridotite. The central unit of the sill is a graded mass beginning with theralite at the top and passing gradually into picrite, and finally peridotite, by gradual enrichment in olivine and elimination of felspar, nepheline, and analcite.
The field detail of the Bellow, Glenmuir, and other sections is given in part ii of the paper; and the petrographic detail, with several chemical analyses, in part ii. A unique rock, named lugarite in 1912, with 50 per cent of analcite and nepheline, occurs as an intrusion into the heart of the ultrabasic mass of the sill. Part iv deais with the special significance of this sill in petrogenetic theory. The mineral and chemical variations are described and illustrated by diagrams. It is shown that the average rock of the sill, obtained by weighing the analyses of the various components according to their bulk, is much more basic than the rock now forming the contacts. Hence, assuming that the sill is a unit and represents a single act of intrusion, the main differentiation cannot have occurred in situ. Other special features of the sill are the identity and banding of the contact rocks, its asymmetry, the density stratification of the central ultrabasic mass, and the sharp junction between the upper teschenite and the underlying theralite.
The theory is advanced: that the differentiation units were produced by the process of liquation, but that their arrangement within the sill took place under the influence of gravity. There are sharp interior junctions between a unit consisting mainly of calcic ferro- magnesian silicates and a unit consisting mainly of alkali-alumina silicates with water, the former giving rise to the central ultrabasic stratum and the latter to the teschenites. These partly immiscible
238 Reports & Proceedings—Minerulogical Society.
fractions arranged themselves according to density. Then within the central ultrabasic stratum there was a subsidiary gravity stratification—due to the subsidence of olivine crystals, giving rise to the graded mass described above. If differentiation had occurred subsequent to the arrival of the sill in the position that it now occupies, the contact rocks should have the same composition as the average rock of the sill. his, however, is not the case, as the average rock has the composition of an almost ultrabasic theralite, entirely different from the teschenites of the contacts. Hence it is believed that, after forming contact-sheaths of theralite, and under- going gravity stratification subject to liquation, the intrusion activity was renewed, and the sill was moved on along bedding-planes into cold-rocks, leaving its contact-sheath behind adhering to the old | contacts, and establishing new contacts with its upper and lower teschenite-layers. Here crystallization began, and, by the subsidence of olivine, the subsidiary gravity stratification of the central ultra- basic layer was effected. ‘The extraordinary flow-banding shown by the contact rocks affords confirmation of the renewed movement thus postulated. .
In conclusion, the sill is compared with five other teschenite- picrite sills in Scotland, those of Ardrossan, Saltcoats, Blackburn, Barnton, and Inchcolm.
II].—MuvyeratocicaL Socrery. March 21, 1916.—W. Barlow, F.R.S., President, in the Chair,
Dr. J. W. Evans: A new Microscope Accessory for use in the determination of the Refractive Indices of Minerals. The accessory— a diaphragm with narrow slit adjustable in width—when placed in the primary focus of the objective or any point conjugate with it, serves several useful purposes. If placed parallel to the boundary between the two substances whose refractive indices are to be compared by the Becke method, it gives better results than an iris diaphragm. In the case of doubly refractive sections or grains in which an axis of optical symmetry lies at right angles to the microscope axis, the slit is placed parallel to the former axis, so that the paths of all the rays of light traversing it lie in a plane of optical symmetry and one direction of vibration is always parallel to the axis of optical symmetry, and a nicol is inserted so that the direction of vibration of the rays traversing it is parallel to the same axis: then the refractive indices of light vibrating parallel to that axis of optical symmetry may be investigated by the usual methods without the confusion caused by the bifocal images described by Sorby.—L. J. Spencer: A Butterfly Twin of Gypsum. In a well-developed twin- erystal, 6inches across, from Girgenti, Sicily, in which the twin- plane is d (101), the two individuals are situated on the same side of the twin-plane instead of on opposite sides as in the usual type.— Dr. W. R. Jones: The Alteration of Tourmaline. In a moist tropical climate minerals which are ordinarily regarded as stable break down to an extraordinary degree. At Gunong Bakau, Federated Malay
Reports & Proceedings— Geological Society of Glasgow. 2389
States, tourmaline is found more or less completely altered to a mica (probably phlogopite) and limonite, the degree of alteration decreasing with increasing depth from the surface, suggesting that the change was caused by the percolation of water from above. The freshness of tourmaline grains in sands is very probably due to the removal of the altered products by chemical and mechanical means.
Il1.—Gzrotoeican Socrrry or Guascow.
Votcanozs in AyrsHire.—At a meeting of the Geological Society of Glasgow, held on March 9, Mr. G. V. Wilson, H.M. Geological Survey, read ‘‘ Preliminary Notes on the Volcanic Necks of North- West Ayrshire’’. The area dealt with lies between Dalry, Ardrossan, and Largs, and has been found to contain the remnants of about thirty voleanoes. ‘The various necks were described, and it was pointed out that they were not all of the same age. While some are probably of Caleiferous Sandstone age and connected with the great Misty Law volcano further north, others were much later as they contained large blocks of sedimentary rocks, including one with a coal-seam which was large enough to be worked within the vent many years ago. This vent must therefore have been in action after the formation of the coals of early Carboniferous times. Fragments of charred wood also occurred, while in one instance sea-shells, which had evidently been washed from the sea-floor directly into the voleano, were found. This showed that the volcano had been either submarine or on low ground liable to submergence, and the shells being of a type not later than Millstone Grit, the age of the vent was approximately fixed thereby. It was pointed out that the ash in the necks was, in some instances, very similar to that which replaces the black-band ironstone over much of the Dalry district, which suggested that it had come from this source, and that activity had continued intermittently until Millstone Grit or later times. It was suggested that in the days of its activity this district had resembled the San Franciscan volcanic field of Arizona. The paper was illustrated by a series of photo- micrographs and views.
Mr. J. V. Harrison, B.Sc., described a section at Tormore, Arran, showing the junction of the two red rock series of Arran, and where no sharp line of division was visible.
CORRESPON DEHN CE.
>
THE GRAINSGILL GREISEN OF CARROCK FELL.
Srr,—Among a collection sent to me last year of small specimens from various well-known rocks in the British Isles was one of the -Grainsgill Greisen, Carrock Fell, described in vol. li of the Q.J.G.S. by Mr. A. Harker. For purposes of comparison with local rocks I have had three sections prepared from this specimen, which was only about 14in. square and } in. thick, and used the remainder for separations in heavy liquids. The quantity of rock available was so
240 Correspondence—J. B. Scrivenor.
small that it is impossible to base any conclusions on the examination, but the following notes may be of interest to anyone who has time and opportunity to examine larger specimens.
The most interesting point observed in my specimen is the abundance of rutile, in the form of ‘‘ sagenite webs’’, in the mica. A separation of powdered rock in a liquid of 2°8 sp.g. afforded a lot of them. They are visible in the slides too, but their abundance is only appreciated in preparations where the mica flakes are lying flat. In addition to rutile I obtained a few grains of brookite and one crystal that resembles anatase. One little plate of brookite, with clear erystal outline, gave a good axial figure. This unfortunately was either lost or turned on edge when mounting the heavy minerals in balsam, but two other minute grains give figures with a 14 in. oil immersion objective.
With regard to the origin of the small-flaked mica I am inclined to think it is certainly derived from the felspar, of which I was able to separate enough for two microscope preparations, and there is evidence too of some of the large-flaked mica being derived from felspar. With regard to that containing the sagenite webs, the latter are unusual in muscovite, in fact I do not remember ever seeing them, and their presence suggests that the mica may originally have been a dark mica which has become bleached, but not completely so. On the other hand, it might be argued against this that the mica containing the webs has an axial angle about equivalent to that of muscovite, but the idea that the rock originally contained a dark mica is strengthened by the fact that some of the quartz-grains enclose minute flakes of biotite.
Apatite and zircon occur, and I found a few minute grains of a mineral like cassiterite. One showed a carmine pleochroism common in cassiterite, although not mentioned in textbooks. I was unable to prove anything, however, about these grains. Some may be sphene.
I found two grains of tourmaline, and tested the mica for lithia with negative result.
J. B. Scrrvewor.
GEOLOGIST’S OFFICE, BATU GAJAH. March 2, 1916.
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Ws ' Tea “Honal Musew™ I.—NoreEs oN NEW OR IMPERFECTLY KNOWN CHALK Potyzoa. By R. M. Bryvons, F.G.S.
(Continued from the March Number, p. 100.) PLATE X. MEMBRANIPORA MISSILIS, sp. nov. (PI. X, Figs. 1, 2.)
Zoarium unilaminate, adherent.
Zoecia strongly pyriporiform, very small, length about -4 mm.; areas broadly speaking elliptical but with a strong tendency to have the upper end flattened rather askew to the central line, average length "18mm., breadth -11mm.; the side walls of the area bear about a dozen tubercles so small that their existence is only just recognizable under a 38 in. objective; a 1 in. objective shows them to be perforated ; below the area there is typically (after the early stages) a small perforated boss placed centrally on the front wall, but when the front wall has to accommodate an ocecium the boss splits into two, often very massive, one on either side of the ocecium.
Owcia very large in proportion, globular but tending to end in a definite but blunt point like an artillery shell; free edge narrowly and deeply concave. :
_ Avicularia vicarious, fairly numerous, consisting of a shallow and wide pan with a small rounded aperture at the lower end; over the lower part of this aperture the side walls are sharply pinched in.
This species appears in the zone of Marsupites in Hants and Sussex, where it is rare, and also occurs very sparingly in the zones of Offaster pilula and <Actinocamax quadratus. It has a superficial resemblance to J. coralliformis, Bryd.,} which is curiously strong considering that their avicularia are the only point of resemblance in detail. z
Memeranipora Fanwia,? sp. noy. (Pl. X, Figs. 3, 4.)
Zoarium unilaminate, adherent.
Zoeeia pyriporiform, of fair size, length about -5 mm.; areas corresponding in shape to those of IL misslis (supra), average length ‘29mm., breadth -2 mm., surrounded by a flat rim which is narrow
1 GEOL. MaG., 1910, p. 259, Pl. XXI, Figs. 4, 5.
2 The difficulty of finding any Latin word at once distinctive and appropriate as a specific name in a genus such as Membranipora, with its hundreds of species already described, is so acute that I have followed the example set by D’Orbigny with Hschara of using classical names. He got as far as H, so I have begun with F.
DECADE VI.—VOL. III.—NO. VI. 16
242 R. M. Brydone—New Chalk Polyzoa.
and sharply marked in the upper part but widens towards the lower end and almost dies away; on this rim are four pairs of tubercles, of which the two highest are prominent and perforated, the third is distinctly less prominent and probably perforated, and the lowest very faint and probably not perforated; just above the upper corners of the area there are sometimes indications of a pair of tiny pores or perforated tubercles; the external front wall bears a small central perforated boss, which may be shifted to one side when the front wall has to accommodate an ocecium, but generally seems to disappear.
Oecva globular, sturdy, with a concave free edge lying well back from the area.
Avicularia, apart from the possibilities of the central boss, do not oceur.
This species is fairly well distributed, though sparingly, in the zone (restricted) of A. quadratus. It has obviously many points of general affinity to Jf. missilis, but no close relationship can be alleged in view of the following species.
Memsranrpora cuponata, sp. nov. (Pl. X, Figs. 5, 6.)
Zoarium unilaminate, adherent.
Zoecia pyriporiform, small, length about -4 to ‘45 mm.; areas slightly elliptical, but almost, sometimes quite, round with an average diameter of :16mm.; round their upper end there are about five small perforated tubercles; after the early stages a perforated boss appears on the front wall and rapidly assumes very large proportions ; when the front wall has to accommodate an ocecium, the boss splits into what appear under a 3 in. objective to be two tubes generally inclined forward and obliquely truncated in the horizontal plane so as to give an elongated section, but under a 1 in. objective prove to be tiny avicularia of the same general type as those of JL. mussilss, highly. exsert, and directed indiscriminately backwards or forwards.
Oecia very striking, narrow, and very long, and ending in a short spike like a dome and cupola; the spike generally projects over the area of the succeeding zocecium and so is very plainly visible.
No vicarious avicularia observed.
This species, which is very compact and thick in appearance, is fairly abundant at ‘'rimingham and occurs also in the Weybourne Chalk. Its surface is so uneven that photographs hardly do it justice. Its affinity with Jf mussilis is obviously very close apart from the avicularia.
MeMBRANIPORA VECTENSIS, sp. noy. (Pl. X, Figs. 7, 8.)
Zoarium ‘bilaminate’, branching, branches generally broad; the central lamina is very thick in proportion to the zocecia, and occupies about three-fifths of the total thickness of the zoarium.
Zoecia lengthily hexagonal, average length ‘55 to ‘6mm., side walls decidedly wide; areas shallow, long and narrow, with a strong tendency to pointed ends especially at the lower ends, and often sealed by a calcareous lid; they generally stop short some way from the lower end of the zoccia, which then have a piriform appearance.
No oecia or avicularia have been observed.
PuatE X.
Grou. Maa., 1916.
S ~ = o Ss MS
iA]
=
Ss va 3
co
Zz) oS
R. M. Brydone phot.
Chalk Polyzoa.
Dr. Cotton—Later Geological History of New Zealand. 243
This species is only known to me from the Isle of Wight, where it occurs all over the island sparingly in the zone of Holaster planus and freely in the Chalk between the ‘ grey marl’ and the ‘ black marl’. It is very near akin to Biflustra lacrymopora, D’Orb.1; but the thick central lamina, the wide and clumsy-looking side walls and narrow _ area, and the total absence, as far as my experience goes, of ocecia seem full warrant for a specific separation which the very restricted horizontal and vertical range, and the great rarity of Biflustrine forms in our Chalk, would tempt one to make on slenderer grounds.
EXPLANATION OF PLATE X. (All figures x 12 diams.)
1. Membranipora missilis. Zone of Marsupites. Well, Hants.
2. M. missilis. Zone of Marsupites. Brighton. i
3. M. Fannia. Zone of A. quadratus. Shawford, Hants.
4. M. Fanma. Part of the same specimen in a different light.
6. M. cupolata. Trimingham.
8. M. vectensis. Zone of Holaster planus. Culver Cliff, Isle of Wg
(To be continued.)
IJ.—Tax Srrevcrvure anp Later Gronogicat History or New ZEananp.
By C. A. Corton, D.Se., F.G.S., Victoria University College, Wellington, N.Z.
Tue Mesozoic Orocenic Movements.
Ae is well known, the skeleton or oldermass? of New Zealand is largely composed of a mass of deformed sedimentary rocks, the ‘precise ages of the members of which are in doubt but do not affect the problem under consideration. The most profound deformation of this vast sedimentary group took place in late Jurassic or early Cretaceous times during what may be termed the ‘‘ Mesozoic orogenic ‘period”’, when probably a great mountain range came into existence. It was the opinion of Hutton * that the mountain range which resulted from the Mesozoic folding still survives in the present-day mountains of New Zealand ; but this view, though accepted by Suess,‘ is not specifically maintained by any modern New Zealand geologist. The contrary opinion has, however, rarely been expressed. *
I Pal. Crét. Franc., v, p. 274, pl. 695, figs. 1-3.
2 The writer employs the convenient terms ‘oldermass’ and ‘ covering strata ’ or simply ‘cover’ in the sense in which similar terms were introduced by W. M. Davis (“‘ Relation of Geography to Geology,’’ Bull. Geol. Soc. Am., vol. xxiii, pp. 93-124, 1912). ‘ Oldermass’ means a mass of rocks, generally of complex structure and of various ages, which have been planed down by erosion and which have been covered, during a later period of Bum eree nee, by a series of “ covering strata’.
3 F. W. Hutton, The Geology of Otago, Dunedin, 1875, p. 10; see also “On the Geology of the New Zealand Alps’’, Proc. Roy. Soc. Tas., 1886.
+ EH. Suess, The Face of the Earth, vol. ee p. 148, Oxford, 1906.
> But see P. G. Morgan, ‘‘ The Geology of the Mikonui Subdivision, North Westland,’’ N.Z. Geol. Sury., Bull. 6, 1908, p.43; and also R. Speight, ** The Mount Arrowsmith District: Physiography,’’ Trans. N:Z. Inst., vol. xliii, pp- 319-20, 1911; ‘‘ The Intermontane Basins of Canterbury,’’ ibid., vol. xlvii, pp. 336-53 (p. 353), 1915. . ik
244 Dr. C. A. Cotton—Later Geological
The folds of this system have sometimes been regarded as trending uniformly north-east and south-west parallel with the elongation of the existing ranges in which the rocks occur,‘ and from this it might be inferred that they determine the north-east and south-west trend
NORTH ISLAND
Kaikoura
lauuR.
HurunuiR
SOUTH ISLAND
ky Lake . WaitakiR RR) Manso. Oamaru
hate VE ora bd; Shag R.
b4 7 Tatert 2,
Fic. 1.—Locality map of New Zealand.
1 See, for example, P. Marshall, ‘“New Zealand and Adjacent Islands,’’ Handbuch der regionalen Geologie, Bd. vii, Abt. i, p. 58, Heidelberg, 1911 ; Geology of New Zealand, Wellington, 1912, p. 127.
History of New Zealand. 245
of the land masses of the South Island and the southern part of the North Island, an inference that has apparently been drawn by Gregory, who includes the coasts of Central New Zealand with those of his ‘primary Pacific type’’?. Such an inference is probably not true for any part of the coast of New Zealand. In the southern part of the North Island—in the vicinity of Wellington, for example—the discordance of the trend of the folds with that of the shore-line is shown clearly by the en echelon arrangement of the ridges which may be noted from any high point of view, ridge after ridge and valley after valley of the subsequent features developed by erosion on these strata being obliquely truncated by the western coast. The trend of the ridges, corresponding with the general direction of the strike of the rocks, is only 10° to 15° east of north, while that of the coast is north-east, parallel with the elongation both of the mountainous axis of the island and of the land mass as a whole. Some of the north-east trending coasts of Central New Zealand have recently been described by the writer as resulting from faulting of comparatively modern date.? In the South Island there appears to be by no means a close agreement between the trend of the major features and that of the folds of the oldermass. Scattered observation of the strike made by the writer in the north-east of the island show that it is very variable, but the average trend appears to be the west of north. Observations by McKay in the same district also indicate great variability,® and both McKay * and Hutton ® have noted a more or less definite dome and basin structure. In the main ranges of the Southern Alps the average strike of the rocks was noted by Dobson to be N. 22° E. (fide Haast). Haast ® and later observers, particularly Morgan” and Speight,® record great variability in that area also. In the study of the major relief features of New Zealand the trend of the Mesozoic folds may be almost entirely disregarded, for these features have been blocked out by much later orogenic movements, and the deformed strata of the oldermass, when affected by the latter movements, have generally behaved like resistant massive rocks.
1 J. W. Gregory, ‘‘ The Structural and Petrographic Classification of Coast
Types © : : Scientia, vol. xi, pp. 36-63, 1912. 2 ** Fault Coasts in New Zealand ’’: Geog. Rev., vol. i, pp. 20-47, 1916.
> A. McKay, ‘‘On the Geology of the East Part of Marlborough, Cole Mus. and Geol. Surv. N.Z., Rep. Geol. Expl., 1885, pp. 27-136, 1886; “On the Geology of Marlborough and South-East Nelson,” ibid., 1888-9, pp. 85-185, 1890.
4 F. W. Hutton, ‘‘ Report on the Geology of the North-East Portion of the South Island ’’: Col. Mus. and Geol. Surv. N.Z., Rep. Geol. Expl., 1873-4, pp. 27-58, 1877 (p. 32).
° A. McKay, ‘‘On the Older Sedimentary Rocks of Ashley and Amuri Counties’’: Col. Mus. and Geol. Surv. N.Z., Rep. Geol. Expl., 1879-80, PP. 83-107, 1881 (p. 85).
® J. von Haast, Geology of the Provinces of Canterbury and Westland, Christchurch, 1879.
eG: Morgan, “The GUD ey. of the Mikonui Subdivision, North West- land,’’? N.Z. Geol. Surv., Bull. 6, 1908; ‘‘ A Note on the Structure of the Southern Alps,”’ Trans. N.Z. nae "vol. xliii, pp. 275-8 (p. 277), 1911.
8 R. Speight, ‘‘ The Mount Arrowsmith District : Physiography ’’: Trans. N.Z. Inst., vol. xliii, pp. 317-42 (p. 319), 1911.
246 Dr. C. A. Cotton—Later Geological
A Perrrop or Erosion AND DeEposttion FOLLOWING THE Mxsozorc Orogenic Movements.
Upon the eroded surface of the oldermass lies a series of covering strata, and there can be no doubt that the mountain ranges which resulted from the Mesozoic orogenic movements had been subjected to erosion throughout a long period and reduced to at least moderate relief before the deposition of the oldest (Cretaceous) beds of this cover. It remains uncertain, however, whether at this stage complete peneplanation had been effected over any considerable area. In North Canterbury, indeed, Speight! has noted changes of facies in the limestone horizon of the covering strata, and there is certainly overlap in the lower beds, indicating that the eroded surface of the oldermass was there still somewhat hilly when submergence began, and that some hills survived as islands during a portion of the period of deposition of the cover. The available evidence points, however, to practically complete submergence of a large part of the north- eastern district of the South Island in the period of deposition of the Amuri Limestone (perhaps Eocene), and in some parts much earlier. The open-water origin and wide original extension of the Amuri Limestone have been demonstrated by McKay * and Hector.* Hector’s brief statement may be quoted: ‘‘ All these formations enter into great flexures that have been eroded to form lofty mountains, and the evidence is complete that they at one time spread continuously over a wide area. ‘This view is therefore completely opposed to the suggestion that has been made that the upper calcareous members of the Waipara formation were deposited among islands and in land- locked inlets after the erosion of the present valley systems.” *
In the Marlborough area there was a long period of uninterrupted deposition extending far into the Tertiary, though to what stage of the Tertiary is not yet satisfactorily established. At this juncture great but quite local uplift occurred in certain areas, probably by block faulting, leading to the deposition in the neighbouring un- disturbed areas of that remarkable formation the Great Marlborough Conglomerate.°®
During the early part of the long period of deposition in Southern Marlborough the neighbouring Marlborough Sounds district to the north and the South-Western Wellington district to the north-east appear to have escaped submergence, for the basal portions of the few small remnants of covering strata, namely, a small area at
-1 R. Speight, ‘‘ The Intermontane Basins of Canterbury’’: Trans. N.Z. Inst., vol. xlvii, p. 350, 1915. °
2 A. McKay, ‘‘ On the Geology of the East Part of Marlborough,’’ Col. Mus. and Geol. Surv. N.Z., Rep. Geol. Expl., 1885, pp. 27-136, 1886; ‘*On the Geology of Marlborough and the Amuri District of Nelson,’’ ibid., 1888-9, pp. 85-185, 1890; ‘‘ On the Geology of Marlborough and South-East Nelson,”’ pt. ii, ibid., 1890-1, pp. 1-28, 1892 (see pp. 5-7).
3 J. Hector, Col. Mus. and Geol. Surv. N.Z., Progress Report for 1885, 1886 ; Progress Report for 1888-9, 1890.
4 Progress Report for 1885, p. xviii.
5 GC. A. Cotton, ‘‘ On the Relations of the Great Marlborough Conglomerate ... 7: Journ. Geol., vol. xxii, pp. 346-63, 1914.
History of New Zealand. 247
Picton! and one in the Makara Valley, Wellington,” are regarded as of Tertiary age. The exposures are so poor in each case that the form of the surface on which the beds were deposited cannot be ascertained. We are not under the necessity of believing that the surface must by that time have been reduced to a plain, for it may have been rejuvenated from time to time by uplift, though adjoiming areas where deposition was in progress were sinking. It is quite possible that portions of these districts have never been submerged since first uplifted by the Mesozoic movements, though the seulpturing to which they owe their present mountainous character followed much later uplift. Planation may well have happened more than once in the long intervening period. North-eastward of Wellington there is no evidence of submergence having taken place until rather late Tertiary times.® Farther to the north, in the centre of the North Islands, Speight * notes the presence of a plateau surface truncating the structure of the oldermass in the Kaimanawa Mountains, which he ascribes to marine erosion. The surface presumably passes under and forms the floor of the Tertiary beds (referred to the Miocene) of that district, which occur up to the height of 8,700 feet above sea-level. It appears probable from Speight’s description that the covering strata were formerly continuous across the island in the Kaimanawa area, and that the plateau of the higher part of the range has been stripped of its cover by erosion. In the south-eastern and north-western parts of the South Island the covering strata, with the exception of some of the basal beds, are mainly marine and of such a nature as to indicate that they -accumulated in an open sea where the supply of terrigenous sediment was very small. Though the total area over which these rocks now occur is not large, their former extension over a much wider area is proved by the presence of outliers. _ From the above considerations and from a general survey of what
is known of the Tertiary rocks it is apparent that during the period of their deposition a great part of the site of the present islands of New Zealand was continuously submerged, and that very little of the remainder was left above water.
It is important to note that the members of the covering strata, whether always strictly conformable or otherwise, appear to follow one another without discordance of dip, no satisfactory evidence to the contrary being known. Thus it may be stated that, except quite locally,® the only movements affecting the region after the
1 A. McKay, Geol. Surv. N.Z., Rep. Geol. Expl., 1890, pp. 153-4.
2 A. McKay, ‘‘ Report on Tertiary Rocks at Makara’’: Col. Mus. and Geol. Surv. N.Z., Rep. Geol. Expl., 1874-6, p. 54, 1877.
3 J. A. Thomson, ‘‘ Mineral Prospects of the Maharahara District, Hawke’s Bay.’’: 8th Ann. Rep. Geol. Sury., Mines Statement, 1915, p. 165.
2 R. Speight, ‘‘ Geological History ’’ in L. Cockayne’s Report of a Botanical Survey of the Tongariro National Park, Department of Land, C. 11, Welling- ton, 1908, p. 7.
5 The hypothetical block movement which has been assumed in order to account for the Great Marlborough Conglomerate has been referred to on an earlier page. In a paper on the ‘‘ Structure of the Paparoa Range’’, read before the Geological Section of the Wellington Philosophical Society,
248 Dr. C. A. Cotton—Later Geological
Mesozoie orogenic period until near the end of the Tertiary were epeirogenic. This is contrary to the view of Hutton,’ who believed that folding movements affected the Cretaceous rocks in early Tertiary times, before the deposition of the remainder of the covering strata.
THe Kaikoura Orogentc Movements.
The orogenic movements which followed the Tertiary deposition, and to which the present relief is entirely or almost entirely due, must have occurred in or about the Pliocene period. The period of movement may be termed the ‘‘ Kaikoura orogenic period ”, since the Kaikoura ranges were the first to be explained by Hector’ and McKay* as owing the whole of their elevation to these late earth- movements. It cannot, however, be definitely stated at present whether the- orogenic movements began contemporaneously all over the region. Far too little is known as yet of the ages and correlations of the members of the covering strata to allow us to arrive at a conclusion on this point.
The immediate cause of the disturbance may have been compression, for, in Central New Zealand at least, compression in a north-west and south-east direction accompanied the movements. In Marlborough the uplifted and depressed areas are elongated with a north-easterly trend, and major faults, some of which are certainly reverse faults, trend in the same direction, as do also folds in the previously horizontal covering strata. Perhaps owing to the rigidity of the oldermass, the strata of which had previously been folded on other lines and would strongly resist the new folding, the region was broken up into a number of ‘blocks’ bounded on one or more sides by faults, folding being generally subordinate to faulting except in the higher members of the covering strata, where the resistance of the rigid floor had least effect.
In recent years, wherever detailed geological work has been done, evidence has accumulated of the importance of the part played by young faults in the structure of New Zealand, as may be found by reference to the accounts of the structure of parts of Westland, Nelson, Otago, and Auckland by Bell, Morgan, Park, Henderson, and others in the bulletins of the Geological Survey, and to a paper by Henderson * in which much information regarding faults in Western Nelson is brought together.
While in a few cases the recognition of these faults rests on the evidence of fault-scarps or fault-line scarps, the majority of the faults described are such as bring the covering strata against the older rocks. Many other faults less easily detected by purely geological August 18, 1915, Dr. J. Henderson stated that in Western Nelson a suc- cession of similar movements had taken place. In these cages, however, during and after the movement, accumulation of sediment went on in the immediate vicinity on an undisturbed sea-floor.
1 Geology of Otago, Dunedin, 1875, p. 76.
* Progress Report, Rep. Geol. Expl., 1888-9, p. liv, 1890.
> ‘*On the Geology of Marlborough and South-East Nelson,’’ pt. ii: Rep. Geol. Expl., 1890-1, p. 7, 1892.
2 dio Hendercen: On the Genesis of the Surface Forms and Present
Drainage-systems of West Nelson ’’: Trans. N.Z. Inst., vol. xliii, pp. 306-15, 1911.
History of New Zealand. 249
methods also occur. The long straight fault-lines shown on the map by McKay’ and the later maps by Park,? connecting up known portions of faults, must of necessity be highly hypothetical, and they probably fall far short of representing the facts; but it is true, never- theless, that to McKay belongs the credit of being the first to recognize the importance of faults in determining the Biya! features and geological boundaries.
McKay’s views are strongly opposed to those of Hutton, who conceived only of regional (epeirogenic) movements of uplift and subsidence in later geological times.* Hutton recognized no young faults and no orogenic movements later than those at the close of the Jurassic except ‘‘a certain amount of folding” restricted to certain localities, which, he believed, took place ‘“‘at the commencement of the Tertiary ”.4
‘* Not only,” he wrote, ‘‘ was the last touch given at this time
commencement of the Tertiary] to the geological structure of the tSouthors Alps, but the chief valleys were also marked out at this period.
‘For example, we find our oldest tertiary rocks occupying the valley of the Waitaki . . . and the Maruwhenua ... Inthe valley of the Shag they extend up nearly to its source... .’°
To the explanation of the geological history of New Zealand thus expressed in 1875 Hutton afterwards closely adhered, as will be gathered from the following statements as to supposed changes in river courses, which are based on the assumption that the present relief has survived from very ancient times. This represents Hutton’s opinion in 1899: ‘‘ The Shag River at one time drained the ‘Maniototo Plains until the gorge of the Upper Taieri was cut.. In early Cretaceous times the Hurunui and Waiau-ua united and entered the sea at Kaikoura. At. a later time they turned down the Weka Pass, and it was not until the Pliocene period that each cut its own valley to the sea. The Upper Manawatu flowed into the Wairarapa, and in the older Pliocene a river ran from the Manawatu gorge to Napier. The courses of all these rivers were changed by the deposition of marine rocks in the valleys, which blocked them; and this, on the subsequent rise of the land, caused the rivers to overflow to one or the other side, according to the position of the lowest opening.” ®
The depressions, such as the Shag Valley and that extending from the Waiau to Kaikoura, regarded by Hutton as eroded valleys and assigned by him in the foregoing passage to ancient courses of various rivers, are more satisfactorily explained as tectonic features which came into existence in the Kaikoura period.
1 N.Z. Rep. Geol. Expl., 1892, p. 1.
2 J. Park, Geology of New Zealand, Christchurch, 1910, pp. 263, 265. * Geology of Otago, Dunedin, 1875, pp. 77-85 and pl. ii. * Loe. cit., p. 76.
> Loc. cit., p. 77; cf. also ‘‘ Sketch of the Geology of New Zealand’’, Quart. Journ. Geol. Soc., vol. xli, p. 196, 1885.
6 ‘«The Geological History of New Zealand’’: Trans. N.Z. Inst., vol. xxxii, p. 180, 1900. (Lo be concluded im our next Number.)
250 Dr. Du Riche Preller—Crystalline Rocks of Piémont.
I1I.—Tae Crrysrattine Rock AR®EAS OF THE Pr&MontESE ALPS. By C. 8S. Du RicHE PRELLER, M.A., Ph.D., M.I.H.E., F.G.S., F.R.S.H. (Concluded from May Number, p. 205.) :
Ill. Tax Dora Riranra Grove. (Figs. 3 and 4.)
|e this group, shown in the sketch-plan Fig. 4, may be included
the interesting pietre verdi areas (1) of the Rocciavré ridge on the right, (2) of Monte Rocciamelone on the left side of the Dora Riparia Valley, and (3) of the Rocciacorba ridge and the Avigliana belt of spurs where the Dora and the Sangone Rivers emerge from the Alps and enter the Po Valley about 20 kilometres west of Turin. —
1. The Rocciavré Area.—This ridge, about 12 by 4 kilometres in length and width, forms the divide between the Dora Riparia and Chisone Valleys, north and south respectively, while its eastern end lies at the head of the short valley of the Sangone torrent which discharges into the Po at Moncalieri south of Turin. Although the ridge derives its name from Monte Rocciavré, the latter (2,778 m.) is only one and not the highest of a remarkable cluster of pietre verdi peaks ranging from 2,600 to 2,900 metres in altitude. Of these the most notable are Rocciavré, Cristalliera (2,801 m.), Pian Real (2,617 m.), and Rocca Rossa (2,891 m.) at the eastern, Gavia (2,841 m.), Rocca Nera (2,852 m.), and Mezzodi (2,777 m.) at the northern, and the highest peak Orsiera (2,878 m.) at the western end, the elevation thus decreasing from west to east. The whole ridge obviously represents a former extensive pietre verdi sheet or cupola cut up by erosion and atmospheric denudation into resistant peaks which are separated by high co/di or saddles of about 2,500 metres altitude.
The high-level pietre verdi area is accessible either from Perosa in the Chisone Valley (700 m.) or from Bussoleno (500 m.) in the Dora Valley, on which latter side the flanks of the ridge are deeply cut by several torrents in cascade gullies or orrzdi.! On the Chisone or southern flanks one of the most remarkable exposures, pointed out by Gastaldi as early as 1876,” is that near Colle della Roussa, about 2,400 metres altitude, where the substratum of minute and tabular gneiss with intercalated crystalline limestone, steatite, and graphitic rock is overlain horizontally and conformably by a great bank of lherzolite more or less altered to serpentine, both compact and schistose, upon which rests an equally high bank of euphodite largely metamorphosed to amphibolic and epidotic rock with smaragdite, and to glaucophanic prasinites. The total thickness of this pietre verdi exposure is at least 200 metres.
Unlike the southern or Chisone flanks, which form part of the gneissic-graphitic zone, the northern or Dora Riparia flanks of the ridge exhibit from Bussoleno (500 m.) upwards the normal
1 These cascade gullies, varying from 100 to 300 metres in height, are characteristic of the mountain-sides of the Dora Riparia Valley, and are locally called orridi both from their weird, forbidding appearance and the enormous quantities of detritus and débris brought down through them by the torrents when in flood.
2 Boll. R. Com. geol., 1876, p. 108.
Fig. 2. SECTION OF MONTE VISO.
iz GLE DAE CS OX St, |
LOY Yin? ZPD
é EX Ditye(geZ
ZZ thn
1:(00,000. OLIN
Sea level. Fig. 3. SECTION OF ROCCIAMELONE. NW,
LL eS:
am Rocccametone ZZ CS
100,000 ALLE, KGL Es fyzse eo bevel, C7, LG Z Fig. 4 THE DORA RIPARIA GROUP. kel fe
Rocciavre, Rocciamelone, Rocciacorba and Avigliana. Roeciamel
if Ue
Wvigtcana Dore Morturnre PY
e © PRocchavee A «(, “lly
fo = il) I) as J
Def DEP,
cs = Calc-schist; cl = crystalline limestone; s = serpentine; e = euphodite; ~ axp = amphibolites and prasinites.
Del. D.R.P.
252 Dr. Du Riche Preller—Crystalline Rocks of Prémont.
crystalline sequence of mica-schist with gneiss intercalations at the lower, and cale-schists with pietre verdi at the higher levels. The Bussoleno gneisses, quarried on the right of the Dora down to Villar Foechiardo, differ greatly from the primitive, large-grained, glandular, eye-gneiss of the Dora—Maira massif which crops out on both sides of the valley from Villar Focchiardo to 8. Michele. Those younger, intercalated gneisses are of the minute and tabular type, in part with porphyroid and eye-structure, more or less tourmaliniferous, often rich in albite and poor in mica, or vice versa, while the mica-schist is frequently garnetiferous.! Such gneiss intercalations also occur higher up the ridge, where they are associated with omphacitic eclogite and prasinite.
The pietre verdi area of the ridge as a whole may be described as composed of peridotitic, serpentinous, and euphoditic masses extending in the shape of a triangular trough from the Orsiera peak at the western to Colle della Roussa at the southern, and to Rocciavré, Pian Real, and Rocca Rossa at the eastern end, while euphodites and prasinites predominate more especially in the Rocca Nera and Mezzodi peaks in the centre of the northern part. The serpentinous masses reach their maximum thickness of about 300 metres in the Orsiera and of 500 metres in the Pian Real peak. The contact between serpentine, euphodite, and prasinite is generally marked by serpentinous, chloritic, and actinolitic schist, and in places by eclogite with large uralitized omphacite crystals, while the chloritic schist, e.g. between Pian Real and Rocca Rossa, contains diallagic, viz. smaragdite, crystals of unusually large size.” The euphodites present a great many varieties and are, as usual, largely altered to their pees and zoisitic derivatives.
In the total rise of 2,300 metres from the valley floor near Bussoleno to the crest-line of the ridge, the garnetiferous mica-schists, with tourmaliniferous gneiss intercalations and quartzite, occupy about 1,200 metres, followed by about 600 metres of cale-schist with intercalated prasinitic and serpentinous schist, and lastly by about 500 metres of pietre verdi forming the cupola of the ridge.
The ravine of the Sangone east of the ridge to Giaveno, where the torrent enters the Po Valley, is deeply and entirely eroded in the gneiss and mica-schist of the Dora—Maira massif without pietre verdi, but in other directions the Rocciavré group is linked with large pietre verdi areas both past and present. Thus, on the north the pietre verdi extend across the Dora Valley to Rocciamelone and the Lanzo valleys, while west, south-west, and south a large number of small intermittent outcrops afford evidence of a former extensive area which lay in the great syncline of the calc-schist formation 20 to 25 kilometres in
1 The gneisses of Bussoleno are among those regarded by Professor Gregory as intrusive and Pliocene (‘‘ Waldensian Gneisses ” : Q.J.G.S., 1894, p. 232 et seq.). His views were traversed in detail by Franchi, si Appunti Monti di Bussoleno’’: Boll. R. Com. geol., 1895, p. 177 et seq., and by Novarese, ‘* Rilevamento Valle Germanasca ’’ : ibid., 1895, p. 277 et seq.; also by Stella, ‘‘ Valli Oreo e Soana’’: ibid., 1894, p. 349, footnote.
2 Franchi mentions such crystals up to 50 ‘centimetres in length. Op. cit., 1895, p. 3 et seq.
,
7 ; »
Dr. Du Riche Preller—Orystalline Rocks of Prémont. 258
width,! and connected the Rocciavré group with the similar groups of Oulx, Chaberton, Genévre, Maurin, Chabriére, and Monte Viso. 2. The Rocciamelone Area.—This imposing mountain, the ancient Mons Romuleus, with its peaked summit rises straight from the Dora Riparia on the right of the valley at Susa (503 m.) to an altitude of 3,537 metres in a horizontal distance of only 7 kilometres. The most accessible ascent is from Susa or, further down the valley, from Bussoleno. The massif lies in the calc-schist horizon, which also includes the series of similar high peaks immediately north of it, as far as the Levanna and Gran Paradiso gneiss massif. From the summit and the sanctuary of Madonna della Neve down the southern flank the cale-schist alternates at first with micaceous schist, lenticular masses of bluish and white crystalline limestone, serpentine with ophicalce or
‘green marble, and amphibolites and prasinites, as far as the spur of
Tre Cresti. From this point in an oblique direction towards Bussoleno and Chianoc, the alternations of calc- and micaceous schist with pietre verdi become more frequent, and nearer the valley floor are replaced by minute and tabular gneiss, intercalated masses of erystalline limestones, and the fossiliferous calcareous beds of Chianoc and Foresto.
On this southern flank, shown in the section Fig. 3, the pietre verdi exhibit remarkable aggregations of amphibolic and prasinitic rocks with both massive and schistose serpentine, which latter becomes so predominant as to eclipse the calc-schist altogether. Especially is this the case in and above the Rio Muletta gorge, which descends to Bussoleno from the Croce di Ferro ridge, and exhibits an almost perpendicular cliff of serpentine no less than 500 metres in height, overlain by another 500 metres of amphibolites and prasinites. The serpentine cliff rests on crystalline limestone which then alternates with calc- and serpentine-schist down to the minute and tabular gneiss near Chianoc, the latter belonging to the same horizon as the
Bussoleno gneisses on the opposite side of the valley. Lower down
the valley, as already mentioned, the typical primitive, glandular gneiss with large elements and greyish-green mica appears on both sides, extending on the left to St. Didero, Borgone, and Condové, and on the right to St. Antonino, Vayes, and the chiusa or defile of S. Michele. In this section of about 12 kilometres the bed of the Dora Riparia is therefore eroded entirely in primitive gneiss, which here forms the northern extremity of the Dora—Maira gneiss massif.
The crest of the great ridge of peaks and crags which runs on the left of the Dora from Rocciamelone eastward for about 36 kilometres to the spur of Monte Musiné, north-east of Avigliana, is almost entirely composed of pietre verdi with only a few narrow outcrops of eale-schist in the intervening eroded saddles or colli. As this ridge forms more properly part of the area of the Lanzo valleys, I shall refer to if again in connexion with that region.
1 The cale-schist formation extends north-west, and entirely encircles the mica-schist and minute gneiss massif of Rocca d’Ambin (3,377 m.), about 20 by 10 kilometres in length and width, which lies between the upper Dora Riparia Valley on the Italian and the Are Valley on the French side, and at
its northern extremity is crossed by the Mont Cenis road from Lanslebourg fo Susa. ;
254 Dr. Du Riche Preller—Crystalline Rocks of Piémont.
8. The Rocciacorba and Avigliana Area (Fig. 4).—This area is of special interest, owing alike to its complex nature and its singular configuration, and also because of its vicinity to Turin, whence it is easily reached by Rivoli, Giaveno, or Avigliana. As already mentioned, the eastern spurs of the Dora Riparia and Sangone Valleys converge to a horseshoe or amphitheatre—about 25 kilometres in circumference and 10 kilometres in width—in the centre of which lies Avigliana. The southern end of the horseshoe, on the right of the Sangone, is formed by the Pietraborga spur (926m.) of the Rocciacorba ridge, the middle or western part by the Ciabergia (1,178 m.) and Sacra S. Michele (962 m.) spurs between the Sangone and Dora Riparia Valleys, and the northern bend, on the left of the Dora, by the promontory of Torre del Colle (600 m.), and the mountain-side comprising, among others, Rocca della Sella (1,508 m.), Monte Curto (1,825 m.), and, at the eastern extremity, Monte Musiné (1,150 m.). Across the centre of the horseshoe, as a connecting link between the Pietraborga and Torre del Colle spurs, stretches the low Moncumi (642 m.) and Avigliana ridge, and between this and the Ciabergia or western spur lie, in an old morainic depression, the two small lakes of Avigliana (452m.). From the Moncumi ridge eastward spread the enormous glacial and alluvial deposits of the Dora Riparia, sloping down towards Rivoli and Turin.’ On the rugged and precipitous flanks of the horseshoe, patches of glacial deposits reach up to 900 metres altitude or 500 metres above the valley floor, but the continuity of the rock formations can be traced all round the crags and in the numerous gullies or orrzdz of the different spurs.
The pietre verdi of this area lie in the horizon of minute gneiss and mica-schists, which are, however, in evidence only in outcrops on the western margin, at the base of the primitive gneiss, and therefore in reversed sequence, as the continuation of the corresponding reversal further south, already referred to. The minute gneiss and mica- schists with crystalline limestone form banks of considerable thickness on the Ciabergia and 8. Michele ridge where they are quarried. Together with the pietre verdi on their eastern margin, they are the continuation of the gneissic, dioritic, and peridotitic belt of the Roccia- corba ridge, which, about 8 by 3 kilometres in length and width and about 900 metres in altitude, extends from Monte S. Giorgio, near Piossasco, on the south, to the Pietraborga spur above Trana at its northern end. The crest-line of this ridge exhibits in succession the masses of garnetiferous and graphitic mica-schist and minute gneiss, lherzolite, serpentine, and dioritie rocks with associated eclogite, and amphibolic and prasinitic schists which constitute the series and reach their greatest thickness in Monte Montagnazza (892 m.).
From the Pietraborga spur the pietre verdi radiate N.W., N., and N.E. in several more or less defined zones, of which the western follows the Ciabergia ridge, crosses the Dora Riparia at 8. Michele, and reappears on the left bank at Chiayrié, while the middle zone, starting from the same point, forms the Moncumiand Avigliana ridge
1 Of this ‘‘ Morainic Amphitheatre of Rivoli’”’, Professor F. Sacco has given an interesting description in Boll. R. Com. geol., 1887, p. 141 et seq.
Dr. W. R. Jones—Topaz and Cassiterite in Malaya. 255
between the Sangone and the Dora, and reappears on the left of the latter at Torre del Colle; andathird zone, bifurcating from the second at the Moncumiridge, crosses the Dora, and, running north-east, forms the Musiné spur. Within the Avigliana horseshoe, the pietre verdi thus attain a visible thickness of 500 metres in Monte Pietraborga, of 700 metres in the Ciabergia ridge, and of 1,200 metres and more on the mountain-side left of the Dora, whence the series continues north for about 25 kilometres along the eastern spurs to Lanzo. It is in this belt that the peridotitic masses, lherzolite and serpentine, with associated euphodite, are more especially predominant. In places, e.g. in the Musiné spur, the lherzolite is so decomposed that it is quarried for the extraction of magnesite.! All the pietre verdi masses of the Rocciacorba and Avigliana area dip at more or less steep angles, in some places are almost vertical, and throughout are much contorted.
The three groups of the Dora Riparia area, viz. of Rocciavré, Rocciamelone (in the triangle Susa, Chianoc, and summit) and Avigliana, including Rocciacorba, cover each about 50, in the aggregate 150 square kilometres, or about 60 square miles, equal to the superficial area of the Monte Viso group. The conclusions as to the age and origin of the pietre verdi groups of Southern and Western Piémont considered in the present paper, will be stated in connexion with the areas of Northern Piémont to be dealt with in the sequel.
1V.—TuHeE Ortern or Toraz anp CassIreRIrE at Gunone Baxkav, Mauaya.
By WILLIAM R. JonzES, D.Sc. (Lond.), F.G.S.
NOPAZ is commonly supposed to have been formed by the action of fluorine-bearing vapours on felspar, but evidence has recently
been advanced with the object of showing that some important veins ‘intrusive in the porphyritic granite of Gunong Bakau, a mountain 4,426 feet high, situated in the centre of the Main Granite Range of the Malay Peninsula, were formed of a rock in which ‘‘ the topaz and cassiterite are not alteration products of previously formed minerals”. The author of this theory gives the rock the descriptive name of ‘ quartz-topaz’, and adds as his reasons for not calling it ‘greisen’ the fact that in places it contains very little mica and that, unlike the majority of greisens, it is not an alteration product.
The writer is very familiar with the area in which these rocks occur, and in a report® written in 1913 called attention, for the
1 The quarried exposure of lherzolite with euphodite and magnesite is on the south-east slope of Monte Musiné, above Casellette (505 m.). About 8 kilom. east of this point, midway between it and Turin, lies, at Pianezza, in the morainiec area, Roc Gastaldi, an erratic monster-block of euphodite measuring 30 by 12 by 14 metres in length, width, and height = 5,000 cubic metres or over 10,000 tons. It is surmounted by a small chapel.
2 J.B. Scrivenor, ‘‘ The Topaz-bearing Rocks of Gunong Bakau’’: Q.J.G.S., vol. lxx, p. 363, 1914.
3 W.R. Jones, Preliminary Report of Mining in the Main Granite Range, Federated Malay States, 1913.
256 Dr. W. R. Jones—Topaz and Cassiterite 1n Malaya.
first time, to their importance as a source of tin-ore. The object of the present paper is to adduce evidence in support of the generally accepted theory for the origin of this topaz and cassiterite, and against that of their primary origin. It is not suggested that topaz and cassiterite never occur as primary minerals, for cases are known where the evidence appears conclusive that they can so occur on a small scale, but for the present attention will be confined to this particular locality, where the occurrence is on a large scale and of economic importance.
The veins of ‘ quartz-topaz’ vary in thickness from about 15 feet
to less than an inch, and in some places have now been extensively worked for tin-ore, notably on the mines of Messrs. Bibby and Ruxton and adjoining mines.
The difficulties against accepting the ordinary theory for the |
genesis of the topaz in these veins are clearly set forth by the author of the paper referred to, and may be summarized as follows: the absence of alteration in the country rock ; the dissimilarity between the vein rock and rock in the same locality that is clearly an alteration rock ; the presence in some of the rock of an iron-rich zinnwaldite which is different from the neighbouring secondary mica; the marked difference between the tin-ore bodies known to be of secondary origin and the bodies of ore in these veins.
The absence of alteration in the country rock in the locality under consideration does not appear to be more pronounced than in other tin-fields where topaz and cassiterite have clearly been shown to be of secondary origin. The dark borders to these veins are stated to be ‘‘the result of reaction between media that came off from the vein rock and the porphyritic granite, and a portion of the original vein rock’’,! and to contain a little topaz and an abundance of tourmaline. Also the granite country rock ‘‘is altered for a few inches by emanations from the vein rock to form familiar pneumato- lytic modifications’’.? This alteration is certainly as extensive as is the case in places at Geyer and Khrenfriedersdorf, areas in the Erzgebirge tin-field, for there the alteration of the country rock is for a distance of only 2 to 6 inches,* whereas in the Graupen area the country rock of the Luxer cassiterite-bearing vein has not been altered at all into greisen.t That the topaz and cassiterite of the Erzgebirge tin-field is of secondary origin has been very con- clusively established, for the mine exposures in Altenberg Zwitterstock show ‘‘that the impregnation has been confined to the upper portion of the granite”’, and that ‘‘at a depth of 700 feet normal granite is encountered, in which zwitter bands are completely lacking or only sparingly present ”’.®
The writer’s observations of various tin-lodes have led him to the conclusion that the amount of alteration of the country rock is
1 J. B. Scrivenor, op. cit-, p. 370.
2 Tbid., p. 375.
3 J. T. Singewald, jun., ‘‘ The Erzgebirge Tin Deposits ’’ : Hconomic Geology, vol. v, p. 267, 1910.
4 Tbid., p. 177.
SV Tbidi pigevaes f
ak we i
Dr. W. k. Jones—Topaz and Cassiterite in Malaya. 257
sometimes extremely irregular even in the same vein, but is greatest,
in general, where the rock contains a network of small fissures filled
with ore. There are, however, exceptions to this, for at the Chendai
and Menglembu lode-veins in Kinta, Malaya, where felspar crystals -are cut by minute cassiterite-bearing fissures, the felspars, as has been previously pointed out by Mr. Scrivenor,'are quite fresh. The writer saw an interesting case at Serendah, Malaya, where the absence of alteration in the country rock of a lode appeared to be due to its coalescence with another lode, exposed later, and through which the mineralizing vapours found an easier conduit.
The dissimilarity between the vein rock and the adjacent alteration rock is only what would be expected, for the rock intruded as veins in the consolidating granite was the more acid part of the differentiated magma and formed, before being subsequently acted upon by an abundance of fluoriferous mineralizers, an aplite or pegmatite vein rich in quartz, felspar, and little or much mica, such as are so very frequent in this neighbourhood. It is not the rule, but rather the exception, to find the peripheries of cassiterite-bearing veins similar in mineral content to the central parts of the vein, especially where the veins are thick. The footwalls of tin-lodes are, in general, richer in ore than the hanging walls and very considerably richer than in the body of the lode; and where wolfram, for example, occurs associated with tin-ore the former frequently occurs sporadically as coarse crystals along the walls. At Zinnwald? quartz and zinnwaldite occur in a lode as layers in such a way that the individual layers are parallel to the walls, and one of these may occur to the almost complete exclusion of the other.
The presence in these ‘ quartz-topaz’ veins of an iron-rich zinnwaldite seems to support, rather than contradict, the secondary origin of the topaz and the cassiterite, for zinnwaldite is also abundant in the veins in the Erzgebirge tin-field. At Zinnwald in this district ‘‘the chief gangue minerals are quartz and zinnwaldite’’.* It will also be shown later that the addition of iron takes place in the process of greisenization in districts where chemical analyses of the greisen and the unaltered rock are available.
Emphasis is given to the marked difference between the ore-bodies occurring at Gunong Bakau, admitted to be of secondary origin, and the ore-bodies in the veins where the topaz and cassiterite are presumed to be of primary origin. The ore-bodies worked at Gunong Bakau occur mainly in four types of lodes: (1) The rock at Hemy’s Lode, which has been described elsewhere* by the writer, is not sufficiently coarse-grained for a typical pegmatite, and although more acid than ordinary granite, is best described as an altered medium- grained granite, very rich in quartz, mica (some being secondary), tourmaline, and cassiterite, relatively poor in felspar, and containing
1 J. B. Scrivenor, The Geology and Mining Industry of Kinta District, Federated Malay States (Kuala Lampur), 1918, p. 62.
2 J.T. Singewald, jun., ‘‘ The Erzgebirge Tin Deposits’’: Hconomic Geology, vol. v, p. 173, 1910.
> Thid.
4 W. RB. Jones, ‘‘ Mineralization in Malaya’’: Min. Mag., vol. xiii, No. 4, p. 198, Oct. 1915.
DECADE VI.—VOL. III.—NO. VI. 17
(
258 Dr. W. R. Jones—Topaz and Cassiterite in Malaya.
a little fluorite; (2) the ‘quartz-topaz’ rock carrying tin-ore and (3) the ‘topaz-aplite’ at Messrs. Bibby & Ruxton’s mine; (4) pegmatite veins, composed mainly of milky quartz, in mines near by.
The differences in the gangue of these lodes do not appear to be more striking than in numerous other areas in Malaya and in other tin-fields, and not even so marked as in some. It might even be said that variations equally great have been observed elsewhere in different parts of even the same lode. ‘The Luxer! vein at Graupen in the Erzgebirge tin-field, for example, is characterized by extremely variable filling. The prevailing gangue is milk-white quartz which locally gives place to coarsely crystallized orthoclase intergrown with albite, and to fluorite; also a dark-green lithia mica and a compact variety of kaolinite (‘steinmark’) occur as subordinate gangue minerals ; and the cassiterite is usually evenly distributed, as in the Gunong Bakau veins. At Zinnwald, in the same tin-field, sulphides are confined solely to the middle of the veins, and the tin-lodes contain as essential constituents quartz and a greenish or brownish-green mica, whereas in the neighbouring area of Altenberg topaz is the predominant constituent. In this tin-field at Sadisdorf a lode?” formerly worked for tin-ore is now worked solely for wolfram and molybdenite. Near the footwall occur large nests of pure wolfram, which together with the enclosing quartz are cut by secondary horizontal stringers of quartz carrying tin-ore and gilberite. These stringers are again cut by still younger vertical fluorspar stringers, and towards the hanging wall a great deal of molybdenite and also a little zinnwaldite are encountered, and bismuth and bismuthine also occur along both walls. .
All the types of rocks found at Gunong Bakau in Malaya are also found in some other tin-fields, notably the Erzgebirge tin-fields, where ‘‘all stages of transformation from granite to greisen are encountered and frequently the greisen areas include unaltered masses of granite’’.* At Geyer the granite is locally converted to a rock containing more than 90 per cent of topaz.‘
It is stated by Mr. Scrivenor ‘‘ that the sequence of events in the mass forming Gunong Bakau is clear. First the porphyritic granite consolidated; then the quartz-topaz veins were intruded; and then the topaz-aplite arrived’’.> If the topaz in the quartz-topaz veins is a primary mineral the differentiation of the original magma must have taken place under extraordinary conditions, for a rock, free from felspar, is supposed to have been intruded after the first, containing porphyritic crystals of felspar, and before the third, which is described as being ‘‘rich in felspar’”’. The absence of felspar in the second intruded rock is explained by supposing that ‘‘in the depths of the igneous mass there was a magma which, if undisturbed, would have crystallized out as a rock composed chiefly of potash
1 J. T. Singewald, jun., ‘‘ The Erzgebirge Tin Deposits ’’: Hconomic Geology, vol. v, pp. 176-7, 1910.
2 Thid., p. 169.
3 Ibid., p. 174.
4 Solomon & His, Zeit. deutsch. geol. Ges., vol. xl, p. 250, 1888.
5 J.B. Serivenor, ‘‘ The Topaz-bearing Rocks of Gunong Bakau’’: Q.J.G.S., vol. lxx, p. 378.
a a
Dr. W. R. Jones—Topaz and Cassiterite in Malaya. 259 felspar”’.! This magma was then invaded by ‘‘a volume of gas. as a huge bubble rising from below, where st had been collected in a part of the magma on which it could not react”, and attacked ‘‘eroups of molecules that would have solidified as felspar if they had not been disturbed by hydrofluoric acid’’? (italics inserted, W.R.J.). The writer will not enter here into the question of the miscibility of silicate minerals in a magma which was sufficiently mobile to be intruded through long narrow veins, some less than an inch thick, nor on the possibility, or otherwise, of the accumulation of a huge bubble of vapour in the depths of an igneous mass, but will point out that no explanation is given of how a highly fluori- ferous vapour can collect in a part of a magma on which it could not react. Moreover, a salic magma depends for its fluidity, as Bowen states,> ‘‘on its ability to retain volatile constituents,” and the presence in such a magma of a free oxide, such as cassiterite, does not appear to be possible.* Especially is this the case in a magma which later emanated hydrofluoric acid.
In a footnote to p. 379 of his paper on these rocks the author has raised a question of great interest. He points out that ‘‘ without segregation one could not expect to have a rock very rich in topaz’’, and gives figures to show that with a pure orthoclase magma only 32°6 per cent of topaz could be formed.
There is, however, an explanation why the percentage of topaz in a greisen does not necessarily depend on the percentage of felspar in the original rock. Researches on greisenization have shown that where it has been possible to obtain analyses of greisens and their neighbouring granites, some of the chemical changes involved appear to be as follows :—
According to Addition of Abstraction of
Vogt.’ Si Oo, Be Os, F (or HF), Sn On, ; CaO, MgO, NagO, and often often also LigO, K2O, and also K20O, Ale Os. perhaps Al O3.
Dalmer.® FeO, F, Sn Oz, and possibly | K,0, Nag O, Si Ox. Ale Os. i Cotton.” Si O02, FeO, MgO, Sn Oz, — Mo Se, Als Os.
Jones, W. BR. | Ale Oz, Sn Oo, Be Os, HF, | KeO, Nag O. : Lig O, and possibly Si Oe.
? J. B. Serivenor, ‘‘ The Topaz-bearing Rocks of Gunong Bakau’’: Q.J.G.S., vol. lxx, p. 379.
2 J. B. Scrivenor, Mining Magazine, February, 1916, ‘‘ Discussion.”
° N. L. Bowen, “‘ The Later Stages of the Evolution of the Igneous Rock’? : Journal of Geology, supplement to vol. xxiii, No. 8, p. 16, 1915.
* A. Harker, The Natural History of Igneous Rocks (London, 1909), p. 166.
° J. H. L. Vogt, ‘‘ Beitrige zur genetische Classification der durch magma- tische Differentiationprocesse und der durch Pneumatolyse instanden Erzyo- kommen’: Zeit. prak. Geol., 1895, p. 146.
* K. Dalmer, “‘ Der Alterberger-Graupener Zinnerslagerstittendistrikt ’” : Zeit. prak. Geol., 1894, p. 319.
7L. A. Cotton, ‘‘ Metasomatic Processes in a Fissure Vein from New England’’: Proc. Linn. Soc. New South Wales, p. 231.
260 3=G. C. Crick—Gigantic Cephalopod Mandible.
Messrs. Fergusson and Bateman,’ as a result of their recent researches on greisenization from different localities, have come to the general conclusion that in the chemical changes involved there is an increase in silica, aluminium (which is only in part Al, O.), and probably of iron oxides, a loss of lime, magnesia, and the alkalies, the losses of the alkalies being approximately in proportion to the amount of each originally present, and only in slight degree selective. The following figures, extracted from analyses of granite and greisens, are instructive. In the cases of veins, the granite country rock would probably, however, be less acid than the former before greisenization.
NEw SouTH WALES.2 ERZGEBIRGE.® GUNONG BAKAU, MATLAYA. Grei Grei Grei é Grei < Unaltered eae Hous a Unaltered Caney pees Unaltered (quakes: aoe Granite. | from vein | Granite. | mica, oe a ‘| Granite. | mica, os aay vein. wall, topaz), | 0P42/. topaz), | 0P22)- SiOg .| 76:69 | 75-42) 78-47| 74-68 | 70-41] 79-73 | 77-12 | 77-50 | 80-08 AlgO3 .| 10-89 | 12-98] 11-50] 12-73 | 13-06") 10-244 11-07 | 13-01 | 12-45 Fee O3 0:76 1:68 | 2-64 — 1-42 \ Air75) | “015 N05 FeO, 0-39 | 0-58] 1-05] 3-00 | 5-09 j Te ae etc. CoNncLusIon.
The topaz-bearing rocks of Gunong Bakau bear striking similarities in their mode of occurrence and mineral content to those found in other tin-fields, and especially to those of Erzgebirge. The. topaz and cassiterite in the latter tin-field have been proved to be of secondary origin, and the evidence appears to be very strong for presuming that these minerals are also of secondary origin at Gunong Bakau.
V.—Norr on a eigantic CepHaLopop MANDIBLE. By G. C. Crick, F.G.S., F.Z.S., of the British Museum (Natural History). [Published by permission of the Trustees of the British Museum. ]
[{\HE British Museum has recently received (in the James W-
Butler collection, presented by his daughter, Miss Daisy Butler) a particularly fine mandible of a gigantic fossil Cephalopod.® Unfortunately the locality of the fossil is not recorded, but as the collection contained quite a number of specimens from Bradford Abbas (Dorset) and the immediate neighbourhood, and the matrix of this specimen agrees very closely with that of those examples, there can be little doubt that the locality of the fossil is almost
1 H. C. Fergusson & A. M. Bateman, ‘‘ Geologic Features of Tin Deposits ’’ : Heonomic Geology, vol. vii, pp. 250-1, 1912.
2 Tbid.,;'p: 241.
3 Tbid., p. 237.
* After deduction of part of Al, which formed 7-86 and 7-57 per cent of these rocks.
> Calculated as Fee Os.
5 British Museum (Natural History), Geol. Dept., reg. No. C. 18659.
G. 0. Orick—Gigantic Cephalopod Mandible. 261
certainly Bradford Abbas, or the immediate neighbourhood, and that the specimen is of Bajocian age.
The fossil (Fig. 2) is obviously the calcareous portion of the upper mandible of a giant Mauwtilus-like animal, as a comparison with that structure in the recent Nautilus pompilius shows.
The mandibles of Wautilus pompilius (see accompanying figures) were described by Sir Richard Owen’ as follows :—
cw a
Fic. 1.—Nautilus pompilius. a, inner view of lower mandible showing the dentated margin of the caleareous upper part; 6, lateral view of the same showing the widely-expanded horny lamine of this mandible; c, lateral view of the upper mandible with its hood-like expansion ; d, inner view of the same, showing the limits of the calcareous extremity of the mandible on the inner side. The calcareous extremities of the mandibles are indicated in figures b,c, d by lighter shading and a light irregular line showing the extent of the calcareous matter. This could not well be indicated in a without interfering with the dentated margin. Natural size. (After A. H. Foord, Cat. Foss. Ceph. Brit. Mus., pt. 2, 1891, fig. 76, p. 364.)
‘hese are two in number, having a vertical motion, and resembling in form the bill of the Parrot reversed, the upper mandible being encased in the lower when closed ; they are adapted posteriorly to a muscular basis, to which they owe their motions. Thus far they resemble the mandibles of the Dibranchiate Cephalopods ; but they are not composed entirely of horny matter, nor are they uniformly of a brown or black colour, their extremities being of a dense calcareous nature, and of a blueish white colour; they are also less pointed at the end; and the oral margins of the lower mandible are notched and dentated.
‘They are proportionately larger than in the Cuttle-fish, each mandible measuring in length one inch and three lines, and in vertical breadth one inch. About half an inch from their anterior extremities the horny part separates into two lamine, the exterior of which in the upper mandible is of little extent (from three to four lines), and is dilated and flattened above so as to form a triangular surface half an inch broad at the base. In the lower mandible the proportions of the two lamine are reversed, the exterior one being produced to the full extent, so as to make it appear larger than the upper mandible, which is not really the case.
‘The calcareous extremities of both mandibles are of a hardness apparently adequate to break through the densest crustacean
1 R. Owen, Memoir on the Pearly Nautilus (Nautilus pompilius), 1832, pp. 20 et seqq.
262 8G. C. Crick—Gigantie Cephalopod Mandible.
coverings, or even shells of moderate thickness. That of the upper mandible is sharp-pointed, and solid to the extent of five lines from the extremity; but in the lower one the calcareous matter is deposited on both sides of a thin layer of the black horny substance and thus a combination of tough with dense matter is obtained, which much diminishes the liability to fracture. This mandible is also more hooked than the upper one, but is more obtuse at the end; it seems from its dentated margin evidently intended to break through hard substances, whilst the sharp edges of the beak of the Cuttle-fish better adapt it for cutting and lacerating the soft bodies of fish. Indeed, in the particulars just mentioned, the mandibles of Wautilus differ from those of every other known species of recent Cephalopoda.”
When found fossilised, usually only the calcareous extremities are preserved, although occasionally portions of the horny substance are found associated with them.!
The present fossil is represented of the natural size in the accompanying figures, and a comparison of them with corresponding figures of the upper mandible of the recent Nautelus pompilius at once reveals the true nature of the fossil; thus, Fig. 2b corresponds to the tip of Fig. 1c, and Fig. 2c corresponds to the uppermost portion of Fig. 1d.
A series of papers on the mandibles of Fossil Cephalopoda has comparatively recently been published by Dr. Alfred Till,’ but the present specimen appears to differ from all the forms belonging to Nautilus-like Cephalopods that have already been described and is therefore regarded as new. Following Dr. Till’s system of nomen- clature the specimen may be named Wautilus (Rhyncholithes butleri, n.sp.) sp., signifying that the name of the mandible is Rhyncholithes butlert and that it belonged to a Wautilus-like Cephalopod of which the species has not been determined.
The present fossil consists almost exclusively of the fossilised calcareous portion of an upper mandible, but it is much larger than any other specimen in the British Museum collection. It bears some remnants of the horny substance of the mandible. In the recent Nautilus pompilius (see Fig. 1c, d) the calcareous portion of the upper mandible consists of a hood-shaped upper portion supported below. by a ‘shaft’. On the inner side the surfaces of these two portions are continuous and more or less in the same plane, but on
1 See A. H. Foord, Cat. Foss. Ceph., Brit. Mus., pt. 2, 1891, fig. 79a (p. 368) and figs. 800, c (p. 369).
2 Tritt (Alfred), ‘‘ Die Cephalopodengebisse aus dem schlesischen Neokom”’ : Jahrb. d. k.k. geol. Reichsanst., Wien, Bd. lvi, 1906, pp. 89-154, pls. iv, v, text-illust.
Tin (Alfred), ‘‘ Die fossilen Cephalopodengebisse’’: Jahrb. d. k.k. geol. Reichsanst., Wien, Bd. lvii, 1907, pp. 535-682, pls. xii, xiii, text-illust.
Tiuu (Alfred), ‘‘ Die fossilen Cephalopodengebisse’’: Jahrb. d. k.k. geol. Reichsanst., Wien, Bd. lviii, 1908, pp. 573-608, pls. xix (i), xx (ii), text- illust.
Triu (Alfred), ‘‘ Die fossilen Cephalopodengebisse ’’: Jahrb. .d. k.k. geo!. Reichsanst., Wien, Bd. lix, 1909, pp. 407-26, pl. xiii, text-illust.
Trib (Alfred), ‘‘ Uber einige neue Rhyncholithen’’: Verhandl. d. k.k. geol. Reichsanst., Wien, 1911, pp. 360-5, text-illust.
G. 0. Crick—Gigantic Cephalopod Mandible. 268
the outer side the median line of the surface of the ‘hood’ makes amore or less obtuse angle with that of the surface of the ‘shaft’. The measurements of the detached calcareous portion of the upper mandible of a recent Nautilus pompilius figured by Dr. Till (1906, pL iy, figs. 1, 2, 3) are: total length, 14°5mm.; breadth, 10:1 mm. ; length of hood (measured along median line of outer side), 10°5 mm. ; length of shaft (measured along median line of outer side), 8°5 mm. ; angle between the hood and the shaft (measured along the median line of the outer side), 98°. Theangle of the apex of the hood as seen from the inner side is 82°.
Fie. 2.—Nawutilus (Rhyncholithes butleri, n.sp.) sp. The type-specimen. a, outer aspect showing the obtuse ridge along the median line of the hood and at h remains of the chitinous portion of the mandible; b, lateral aspect, showing at p a series of shallow pits caused perhaps by a fringed lip, and at # remains of the chitinous portion of the mandible; c, inner view showing the median protuberance. Natural size. Most probably from the Inferior Oolite of Bradford Abbas (Dorset) or of the immediate neighbourhood. Original in British Museum (Nat. Hist.), London, Geol. Dept., No. C. 18659. é
The present specimen is incomplete both at the apex and at the hinder end, so that only approximate measurements are possible. They are: extreme length, 51:7 mm.; breadth, 35:6 mm. ; length of hood (measuredalong the median line of the outer surface), 38-6 mm. ; length of shaft (measured along the median line of the outer
264 G.C. Crick—Gigantic Cephalopod Mandible.
surface), 33°2mm. Viewed laterally the median line of the hood is feebly convex; that of the shaft feebly concave, especially the portion near the hood. The ‘ profile-curvature’ angle, or the angle which the median line of the ‘hood’ makes with the median line of the ‘shaft’, is 94°. The hood has a prominent obtuse median ridge, the sides of the hood forming an angle of 109° with each other. Near the anterior and inner border there is a series of longitudinally- elongated pits, closed anteriorly but open posteriorly, that may perhaps have been caused by a fringed lip such as was described by Sir Richard Owen in the recent Vautilus pompilius,! and on the posterior portion of the hood there are some coarse obscure longi- tudinal ridges. The outer surface of the shaft bears both longitudinal and transverse feeble rounded ridges, giving the surface an obscurely reticulated appearance. On each side of the shaft close to the hood there are remains of the chitinous portion (marked / in figs. 2a and 6)
of the mandible. Viewed laterally the inner surface of the mandible |
is feebly sigmoidal, the anterior portion being concave and the posterior part convex. The anterior two-thirds of this surface is occupied by a protuberance which is widest at its posterior part, being there about 10 or 11mm. wide, and anteriorly narrows and also becomes much less prominent. The hindermost part of the inner surface has several deep irregular depressions. The angle of the hood as seen from the inner side is 61°.
As to the affinities of the fossil, it most nearly resembles the specimen which d’Orbigny? described and figured in 1825 from the Corallian rocks of the Chez promontory, near La Rochelle, France, under the name of Rhyncholithes giganteus, and which was found in the same bed as a large Nautilus, which he named JVautvlus giganteus, that attained a diameter of 18 or 19 inches and was the only Cephalopod found in the bed which yielded the mandible. According to d’Orbigny’s figures that specimen was longer and narrower than the present eamiplel: its extreme length and breadth being 54°8 mm. and 31°2mm. respectively, the angle at its apex, as seen from the inner side, being 48°; also the swelling on its inner surface extends farther backward than in the present example.
We are then led to ask if any Inferior Oolite Nautilus is known sufficiently large to have owned such a mandible. Dr. Foord and the present writer ‘described ® in 1890, under the name Wautilus ornatus, a species of WVautilus from the Inferior Oolite that attained a considerable size, for the British Museum collection contains an example‘ [ No. C. 578] of the species 16 inches in diameter from a quarry near Oborne Church, near Sherborne, Dorset, and another 2 feet in diameter from the Inferior Oolite of Sherborne [_No. C. 3193}. he mandible above described might then have belonged to a large example of such a species.
1 R. Owen, op. cit., p. 22. A Soa similar series of pits is figured by Foord (Cat. Foss. Ceph. Brit. Mus., pt. 2, 1891, figs. 78d, e, f) in an upper mandible from the Lias of Lyme Regis, that Dr. Till has subsequently (Jahrb. d. k.k. geol. Reichsanst., Wien, Bd. lvii (1907), Hft. 3, p. 539) named Nautilus (Rhyncholithes punctatus) nom. nov.
2 A. d’Orbigny, Ann. Sci. nat., ca v, 1825, pp. 215-17, pl. vi, Be) Li
3 Ann. Mag. Nat. Hist., [6], vol. v, p- 273, fig. 7.
* Presented by George Potter, Esq., . R.M.S.
ae
Arthur Holmes—Radio-actiwity. 265
VI.—Ranio-acriviry and THE Earru’s THEerMaL History.
By ARTHUR HOLMES, A.R.C.S., D.1.C., B.Sce., F.G.S.
PART Tit.! Radio-activity and Isostasy.
14. Isosratic CompENsATION.
f¥\HE distribution of land and sea implies that the earth’s outer shell is in a condition of approximate hydrostatic equilibrium. Otherwise the equatorial regions should be girdled by a continental protrusion, or else each of the polar regions should be occupied by a continental bulge. The observed fact that the inequalities of the earth’s surface exhibit neither of these conditions proves that the general ellipticity of the lithosphere does not differ greatly from that which would be assumed by a liquid spheroid having a similar distribution of density in depth. The incapacity—thus demonstrated —of the lithosphere to endure permanent stresses leads naturally to an inquiry into the conditions that maintain continents and mountain ranges above sea-level. Investigations based on the deviations of the plumb-line from the vertical and on the varying intensity of gravity indicate beyond doubt that the elevated tracts of the globe owe their support to a deficiency of density in their deep-seated foundations, while the great sunken areas owe their depression to a corre- sponding excess of density in the underlying rocks. Thus has arisen the conception of zsostasy, a word which was coined by Dutton *in 1889 to express the state of hydrostatic* balance that maintains in position elevated and depressed columns of the lithosphere. Columns of equal cross-sectional area, though of different heights, may have the same mass on account of their respective densities, and if so, at a certain level beneath the mean surface of the geoid, each one will exert the same pressure on the zone below. The regional perfection of isostasy, and its local limitations, have been. demonstrated by the geodetic observations of nearly seventy years. Petit,°in 1849, found that the Pyrenees deflected the vertical much less than was to be expected. Archdeacon Pratt,®.in 1852, discovered a similar anomaly in the case of the Himalayas; and during the later months of the same year Airy,’ then Astronomer Royal, propounded a theory of compensation explaining the anomalies in terms of underlying density. Putnam and Gilbert® established a considerable degree of isostatic equilibrium for the United States in 1895, and their conclusions have been verified in still greater detail
? Parts I and II appeared in the GEoL. MaG. for February and March, 1915, pp. 60-71, 102-12.
= Tat. Jeffreys, “ The Mechanical Properties of the Earth’? : The Observatory, 491, p. 348, 1915.
3 Bull. Phil. Soc. Wash., xi, p. 53, 1889.
* Or hydrodynamic ? ?
° C.R,, vol. xxix, p. 730, 1849.
6 Phil. Trans. Roy. Soc., vol. exlv, 1885.
” Thid.
8 Bull. Phil. Soc. Wash., xiii, p. 31, 1895.
266 Arthur Holmes—Radio-activity.
by the laborious studies of Hayford and Bowie.’ In India,? along the margins of the continents* and over the ocean basins,‘ a similar but less intimate association between terrestrial relief and underlying density has been recognized. At least for the broader features of the earth’s topography the theory of isostasy may therefore be Tee as established.°
15. Lrrirs or Isosraric EQuinisRium.
Hayford and Bowie, in their analysis of the results of the U.S. Geodetic Survey, found that by introducing the conception of isostatic compensation they were able to reduce deflection anomalies and gravity anomalies to respectively one-tenth and one-quarter of the value these anomalies would have had without applying the compensation hypothesis.
The depth of compensation which most successfully reduces the anomalies is 122 km., though it should be noticed that the depth chosen may range from 66 to 305 km. and yet give an almost equally good reduction. Hayford suggests that ‘‘ the maximum horizontal extent which a topographic feature may have and still escape compensation is between one square mile and one square degree ”’ (op. cit., 1906, p. 169). This conclusion implies that the earth’s crust is so weak that the weight of accumulating sediments on the sea floor may well cause the latter to sink. Barrell, however, has made a careful study of the Nile and Niger deltas, and deduces from their thickness and great areal extent a much stronger crust than is possible on Hayford’s view of local compensation. Moreover, he demonstrates that the geodetic results of the United States, ‘‘instead of indicating local compensation to limits of less than one square degree, show on the contrary a ready capacity of the crust under the United States to carry over areas of from 5 to 10 or 15 square degrees, and exceptionally over even larger areas, departures from equilibrium greater than the mean” (op. cit., 1914, p. 165). Barrell supports his view of a strong crust by citing the immense departures from isostatic equilibrium exhibited by areas in India, Japan, and Norway, by the great basaltic dome of Mauna Kea, and by the Tonga Plateau and Deep. That the strength so manifested is greater than that of the surface rocks is only to be expected, for the experiments of Adams have proved beyond question that granite, for example, becomes increasingly stronger with increase of pressure.° There can be no doubt that North America is at present in a state of much
1 Hayford, Proc. Wash. Acad. Sci., vol. viii, p. 25, 1906; U.S. Coast and Geodetic Survey, 1909 and 1910; Science, vol. xxxiii, p. 199, 1911. Hayford and Bowie, U.S. Coast and Geodetic Survey, 1912, Spec. Pub. 10. Bowie, U.S. Coast and Geodetic Survey, 1912, Spec. Pub. 12; Am. Jowrn. Sev., vol. xxxiii, p. 237, 1912.
2 Burrard, Survey of India, 1912, Prof. Paper 12; Crosthwants Survey of India, 1912, Prof. Pap. 13.
3 Schidtz, Skrift. Vedensk. Selsk. Christiania, 1908, No. 6.
+ Hecker, Veréff. k. Preuss. geodat. Inst. Berlin, 1903, No. 11; 1908, No. 12. See also Bauer, Am. Journ. Sci.; vol. xxxi, p. 1,1911; vol. xxxiii, p. 245, 1912.
° Gilbert, U.S.G.S., 1913, Prof. Pap. 85-C. Barrell, Jowrn. Geol., vol. xxii, Nos. 1-8, 1914; vol. xxiii, Nos. 1, 5, and6, 1915.
§ Journ. Geol., vol. xx, p. 97, 1912.
re a Se ee eee at
Arthur Holmes—Radio-activity. 267
more perfect isostatic equilibrium than are most areas of the earth’s surface, and the evidence it affords of the strength of the earth’s crust is therefore insufficient and inconclusive. Barrell justly concludes that ‘‘Isostasy . . . is nearly perfect, or is very imperfect, or even non-existent, according to the size and relief of the area considered ”’. For the continents and oceans the degree of adjustment is high ; within areas of 250 km. in diameter the departure from equilibrium may be high; while individual peaks and even small ranges may be wholly supported by the rigidity of the underlying rocks.
16. THe AstHENOSPHERE.
Barrell has shown that the greater departures from isostasy impose very considerable stress differences on the zone of compensation, and he has applied this fact to a deduction of the strength of the litho- sphere at various depths. If a series of wave-like curves represent the profile of uncompensated hills and valleys, or of oceanic islands and troughs, then the maximum stress difference is imposed at a depth of 1/27 of the wave length. In various parts of the world such wave lengths can be approximately measured. For example, in the ridges and troughs of the Pacific the wave lengths are from 300 to 500 km. Even if the strains set up by these loads were entirely unmitigated by compensation, the maximum stresses would not be applied at depths greater than 80 km. That is to say, the existing inequalities which lack complete compensation are responsible for loads that are almost wholly borne by the zone of compensation as defined by Hayford. Greater inequalities of topography would, if uncompensated, throw stress differences to correspondingly greater depths, and the -fact that such inequalities do not exist unless they are largely or wholly compensated implies that the rocks below the zone of ‘compensation are too weak to support them. Otherwise, if the rocks were rigid enough to support great mountain ranges, why should _the latter be compensated at all? It is a natural conclusion that the lithosphere (limited at its base by the bottom of the zone of compensation) is strong, especially in its upper half, compared with the underlying zone. For the latter Barrell proposes the name asthenosphere—sphere of weakness. The evidence he brings forward leads him to suggest the following approximate figures, to illustrate the variation of strength with depth (op. cit., 1915, p. 44) :—
Depth in Strength in kilometres. percentage. 0 100+ 20 400 Lithosphere é 5 ae 50 25 100 ele 200 8 Asthenosphere 300 5 400 4
The relative weakness and plasticity of the asthenosphere is capable of a second proof based on the implications of isostasy. Denudation
1 At the surface strong limestone or granite can sustain a stress difference of 25,000 pounds per square inch (1,750 kg. per sq. cm.).
268 Arthur Holmes—Radio-activity.
involves a paring away of the upper surface of the lands, and an accumulation of the resulting debris around their borders. The land columns become lighter; the sea floor is weighed down. An equally certain fact, attested by many an eloquent chapter of geological history, is that during the transfer of load from continent to ocean floor the former rises and the latter sinks. What is the hidden mechanism that restores the isostatic balance? Corresponding to the lateral movement of sediment there must be a lateral counter- movement in the rocks far below. At first Hayford considered that this undertow took place within the zone of compensation, but Barrell’ has convincingly shown that this view is untenable, and Hayford? in his latest pronouncement has apparently abandonedit. ‘he undertow must be below the zone of compensation, and consequently the matter at greater depths must be somewhat plastic. Moreover, to maintain an isostatic balance between segments of the lithosphere so extensive as continents and ocean basins the plastic zone—the asthenosphere— must be very thick, certainly several hundreds of kilometres.
Quite independent evidence comes from another branch of geophysics. Tt has sometimes been assumed that a viscous magmatic zone might exist within the earth between a rigid crust and a rigid core. Schweydar * has tested this theory by analysing the results of earth- tide measurements made with the horizontal pendulum. He proved conclusively that a magmatic zone of the kind imagined could not exist, and showed that the results pointed—as one alternative—to the existence of a slightly plastic zone extending downwards from a depth of 120 km. and fading out some 600 km. below.
The existence of the asthenosphere is thus supported by arguments based on three different lines of investigation. In the remaining part of this paper its existence will be accepted, and used asa criterion by which to test the distribution of temperature within the earth that was deduced in Part II.
17. Tue Temperature Curve TESTED BY Isosrasy.
The temperature at any depth below the earth’s surface has been regarded as the sum of three components—(1) that due to the initial temperature at or near the surface, and since modified by cooling ; (2) that implied by the variation of the fusion-point with depth, as controlled by pressure; and (3) that due to the local distribution of the radio-active elements. — |
These three components are mathematically expressed for an depth 2 in equations 9 and 18 on p. 111 of Part II (March, 1919). In calculating the list of temperatures there tabulated, it was. assumed that the downward increase of temperature due to pressure was 0:00005° C. per cm., or 5° C. per km. Such an assumption cannot, of course, be applied satisfactorily to any considerable depth. We do not know to what extent the law connecting pressure with a rise of the fusion-point of a mineral is linear, and moreover the distribution of minerals in depth cannot be a simple continuation of
1 Barrell, op. cit., p. 677, 1914. 2 Hayford, Proc. Am. Phil. Soc., vol. liv, p. 298, 1915. 3 Verdff. Preuss. geodat. Inst., No. 54, 1912.
Arthur Holmes—Radio-activity. 269
what is observed at the surface. If, therefore, the pressure component could be left out of the discussion altogether, and a disturbing factor thus avoided, a considerable advantage would be gained. Now, for the present purpose, this can readily be done, for it is required to compare the fusion-points of certain minerals and rocks! with the temperatures at depths appropriate to their occurrence within the earth. Let us suppose that for a given mineral or rock the rise of the fusion-point at a depth 2 is mx. Then the pressure component of temperature at that depth willalso be mz. The fusion- point may be expressed as S + mx where S is the fusion-point at the surface, and the temperature as 7’+ mx where 7'is the temperature due to other factors than the pressure component. Consequently, in plotting fusion-point and temperature curves the differential relation of one to the other will not be affected by plotting S and 7’respectively instead of S + mx and 7+ mz. Thus, at every depth, «, the appropriate but at present unknown value of mz, may be omitted without detriment, and with the advantage that a doubtful extra- polation is completely avoided.
1800;C Pa Sy SEES NWS EE PG EE I Si barn ip MR nL MCS ON CM Ree eG LE {600 : Enstatite Olivine Diopside 1200} abradorite r 800° F ~ x " ‘\ 400° <i : 5 XN x i » I Depth in Kilometres . °o 100 200 Zi 400 500 600 700
Fic. 1.—The distribution of temperature in depth in relation to the fusion- points of minerals. _ I. Temperature gradient due to radio-activity and the earth’s initial thermal condition in the respective ratio of 3: 1. Ii. Temperature gradient due to the earth’s initial thermal condition alone. Ill. Temperature gradient due to radio-activity alone.
In each ease the pressure component mx is omitted.
In the adjoining diagram the temperature 7’ is plotted in degrees Centigrade against depth in kilometres. Curve I represents the distribution of temperature based on the discussion in Part II (omitting the pressure component mx); thatis to say, the temperature gradient is considered on an average to be due to radio-activity and secular cooling in the ratio of approximately 3 to 1. Curve II
1 By the expression ‘‘fusion-point of a rock’’ is meant the minimum
temperature at which the whole of the rock passes into the non-crystalline condition.
270 Arthur Holmes—Radto-activity.
represents the distribution of temperature in an earth which has cooled down for 1,600 million years from an initial temperature at or near the surface of 1,000° C. Curve II] represents the distribution | of temperature due to radio-active elements alone, and here ma is subtracted from the value at every depth x on the assumption that mis 5° per km., in order that the curves may be comparable. The maximum temperature due to radio-activity could not, on an average, exceed 800° C. + mx.
Since the pressure component is omitted, the fusion curves of minerals become straight lines parallel to the base, i.e. having for every depth the same ordinates. The point of intersection of, say, the labradorite line with any of the temperature curves gives the depth at which labradorite would fuse. Clearly, if none of the earth’s heat were due to radio-activity (curve IT), or if all its heat were due to radio-activity (curve III), none of the minerals represented in the diagram could fuse at all, whatever the depth. The temperature at which basalt fuses cannot be safely put below 1,200° C., and hence basalt magma, and for a similar reason peridotite magma, could not be produced under the conditions of curves II and III. Volcanic phenomena therefore bear witness to the verity of some such curve as I, and indeed curve I expresses almost the maximum temperatures that can occur in depth over wide areas and yet avoid the impossible extremes of universal vulcanism and no vulcanism.
Curve I implies that basalt magma cannot usually be produced at ~ a depth of less than 140 km. But can basalt be supposed to exist at all at such adepth? The distribution of the radio-active elements indicates that it cannot. Indeed, even at a depth of 40 km.! basalt —or whatever may there be its equivalent—could not hold as much uranium and thorium as the basalts which have reached the surface, for if it did so the temperature gradient would certainly be higher than it is. ‘The great majority of the basaltic material of the earth seems, in fact, to be confined to an outer shell of about 30 km. in thickness. Below that depth, the peridotite minerals cannot hope to find a temperature at which they could melt within 200 or 300 km. of the surface. Beyond depths of this order peridotite may begin to approach its melting-point, and thus to attain the possibility of plastic flowage, but it is clear from curve I that actual fusion is not likely anywhere to be a widespread condition. If at any time fusion did become possible the fluid material would be squeezed out to higher levels, leaving a concentration of the unfused materials. It is therefore to be expected that the more fusible ferriferous olivines have long ago been expelled from the interior, leaving behind varieties richer in magnesium, accompanied perhaps by such refractory accessories as chromite. This view is strongly supported by the fact that ferriferous olivines are, on an’ average, richer in radium than those in which the forsterite molecule predominates. As between hypersthene and enstatite the same rule holds.
Barrell’s views as to the physical condition of the asthenosphere are therefore seen to be completely in accord with the temperature
1 70 km. would be the maximum depth possible if the continents were not capped with granites.
Arthur Holmes—Radvo-activity. OT
distribution expressed in curve 1. The weakest part of the outer regions of the earth must be located below the zone of compensation, and this conclusion may be used as an additional argument in favour of the existence of an asthenosphere, or, accepting the asthenosphere, it may be used as a rough corroboration of the distribution of temperature here advocated.
18. VuLCANISM IN RELATION TO MouNTAIN-BUILDING AND RIGEFACTION.
It may be thought that the preceding discussion leads on to the deduction that, whatever vulcanism may have gone on in the past, none ought to be possible at the present day. This is not so, for until now an average distribution of the radio-active elements has alone been considered. In relation to worldwide phenomena such as the maintenance of isostasy between continents and oceans, the use of average conditions is justified by the broadness of the problems involved. In relation to more localized phenomena such as mountain- building, block faulting, and vulcanism, departures from average conditions become critically important. The departures may, of - course, be of two kinds, those in which the distribution of the radio- active elements and the dependent temperatures in depth are locally in excess of the average, and those in which the radio-active elements and deep-seated temperatures are deficient.
Let us consider the first of these cases. In regions of heavy sedimentation, a thick blanket of rocks considerably richer in radium and thorium than basalt (Part I, p. 63, February, 1915) is super- imposed on the previously existing ‘‘radio-active layer”. As _ Professor Joly has shown, when ‘‘ we take into account that in the radium content of the sediments there is a source of heat competent to bring the geotherms closer to the surface in the region of deposition than elsewhere in the surrounding crust ”’,' the possibility of weakness and even of fusion at moderate depths becomes clear. ‘The rise of temperature at and below the base of the accumulating sediments is much greater than one would think possible, for the basal temperature due to radio-activity is proportional to the square of the thickness of the uniform radio-active layer above it. ‘To illustrate the effect by a concrete example, let us take the figures referring to average igneous rock given on pp. 66 and 67 of Part I (February, 1915). Ifthe distribution of radio-activity were uniform the depth of the radio-active layer would be 30 km., and the basal temperature 570° C. The addition of a thickness of 10 km. of sedimentary rock would then increase the thickness of the radio-active layer to 40 km. and the new basal temperature would become 1,005° C. (30? : 40?= 570: 1005). Since the distribution of radio-activity is not uniform, but decreases in depth, and therefore continues to much greater depths than 30 km., so the rise of temperature due to sedimentation is considerably greater than that given in the calculation just made. An exact calculation of the effect on an exponential distribution would be difficult, if not impossible, but the magnitude of the rise in temperature may be appreciated by considering only the outer 10 km.
1 Radio-activity and Geology, 1909, p. 94; see also The Birth-time of the World, 1915, p. 116 et seq.
212 Arthur Holmes—Radio-activity.
shell. Normally its temperature due to radio-activity is 264° C. (p. 111, Part II, March, 1915). The addition of a 10 km. blanket of sediment would increase this temperature, now at a depth of 20km., to over 1,000°C. (10? : 20? = 264: 1056). The association of volcanic eruptions with sedimentation and the weakening of the crust preparatory to the upheaval of mountains along lines of heavy . sedimentation thus becomes easily explicable.
The second case—that involving a deficiency of radio-activity— applies to areas which have undergone long denudation and have thus been deprived of part of their most richly radio-active rocks. If isostasy also comes into play, then regions originally at a consider- able depth and temperature may become exposed at the surface. Combined cooling and uplifting gives a double reason for the development of tensional stresses. Thus areas like Africa are rigefied and strengthened by cooling, and rent asunder by contraction and uplift. The existence of structural features such as rift valleys implies the development of tension clefts reaching down to considerable depths. ‘This in turn implies local relief of pressure and a corre- sponding reduction of the temperature at which the rocks below can attain fusion. Here, then, although the surface phenomenon is one of cooling and rigefaction, the effect in depth is to promote fusion, and vulcanism is again made possible. It thus appears that igneous activity may be controlled by two totally different classes of phenomena; in some regions by radio-active superheating, and in others by far-reaching relief of pressure. It is to be expected, then, that the mechanism of intrusion should be notably different in the two cases, and that at least partial differences in the composition of _ the resulting rocks should be observed between them. We have here a physical explanation for the undoubted core of truth contained in the conception of ‘ Atlantic’ and ‘ Pacific’ types of igneous rock— a conception that errs in detail rather than in principle; and one that has suffered by the rigidity of its expression rather than by its lack of verity. It is hoped in later contributions to this series of articles to discuss earth movements and their appropriate igneous associations in the light of the considerations briefly outlined above.
8 19. Isosrasy AND THE AGE oF THE HARTH.
The title of this article provides the author with a suitable opportunity for discussing a recent paper by Dr. G. F. Becker.’ In it Dr. Becker correlates. recent developments in isostasy with others arising from the application of radio-activity to geological problems. He assumes that the undertow by which isostasy is maintained takes place at the basal level of isostatic compensation (1.e. at the depth of, say, 121km.), and that this level must also be the ‘‘ eutectic level ” at which fusion can most easily be accomplished. The ‘‘ eutectic level” 2, is calculated from the following equation connecting 2, and ¢, the age of the cooling earth :—
ha rt (V— =O) ham ety [anPt (14) 0-017 V 1 ““ Tsostasy and Radio-activity’’: Bull. Geol. Soc. Am., yol. xxvi,
pp. 171-204, 1915.
Arthur Holmes—Radio-actwrty. 273
The symbols are those employed in Part II (p. 108) except that V is the initial surface temperature of the earth, taken by Becker as 1,300°C., and 6 is the melting-point of diabase at the surface, taken on the authority of Barus as 1,170°C. Solving with Becker’s data and giving definite values to z,, the following are some of the results obtained :—
%1, the depth of The proportion of the titheraceor the
cate ean. aa eae ear earth in years. 121 0-1425 68 million. 180 0-43 200 a 254 ‘ 0-59 600 a5 300 0-6667 MSA Ay 315 0-675 1,600 55
Tf 2, is actually the depth of the level of isostatic compensation, as Becker believes, then the age of the earth is 68 million years according to this calculation, and only one-seventh of the earth’s heat can be maintained by radio-activity. -The impossibility of the latter result itself throws doubt, if indeed it does not disprove, the validity of the whole method. Curiously enough, however, the calculations show that if the level at which isostatic restoration most readily takes place is at a greater depth than 300 km., then the age is either about that required by radio-active minerals or is considerably higher. The work of Barrell on the strength of the earth’s crust, and of Schweydar on tides in the solid earth, suggest that the depth of flowage in question actually is greater than 300 km., and the quite independent results of this paper are in complete accord with such a conclusion. So far from disproving the great age of the earth imphed by radio-active methods, Becker’s analysis would seem to lead to an equally high or even higher age. But it may be noticed that the value of ¢ derived from any stated value of x, in equation 14 is strongly affected by the value of V—b. Thus the results are vitiated at their very source, for the figure chosen for V, viz. 1,300°C., is a pure guess. Any other figure would give totally different values for ¢.° Moreover, the equation fails altogether to give a rational result if ( V—0) is not positive ; that is to say, unless the initial surface temperature of the earth were higher than the melting-point of whatever rocks are in place within the asthenosphere. Already Becker’s paper has been quoted as furnishing an argument against the radio-active methods of determining time. Clearly it fails to do so for the following reasons :—
(1) The value assigned to Vis a pure guess.
(2) The depth of the ‘‘ eutectic level’’ is said to be at the level of isostatic compensation instead of 200-800 km. below that level.
(3) The proportion. of the temperature gradient maintained by radio-activity cannot, on the age favoured by Becker, be more than one-seyenth of the whole.
(4) It is assumed that ‘ diabase’ can be present at a depth of
Ao! Qi ema
(5) If the method were valid it would imply that the earth had
cooled for considerably longer than 1,600 million years. DECADE VI.—VOL. Il.—NO. VI. 18
274 Reviews—The South Wales Coalfield, Milford.
20. Concxusions or Part III.
1. Barrell’s investigation of the strength of the earth’s crust, based
on geological, geodetic, and geophysical data, indicates that the depth of maximum flowage by which regional isostasy is maintained les within the asthenosphere at a depth far below Haye level of eelamaace The distribution of temperature in depth (due sic to radio- ee energy and partly to the initial thermal state of the earth) deduced in Part II is fully in accordance with the mechanical status oe to the asthenosphere. Mountain-building and associated igneous activity are localized by “the radio-active blanket of deep sedimentation. 4. Rigefaction and tensional faulting and associated igneous activity are localized by denudation and relief of pressure. 5. Becker’s latest method of calculating the age of the earth is invalid, and, if it were not, would lead to a figure for the age of the
earth as great as that suggested by lead-uranium ratios, or to one —
even greater.
REV IWS.
I.—Memoirs oF THE GEOLOGICAL SURVEY.
Tue Grotocy or tHE Sourn Watxs Coarrrerp. Part XII: Tue Country AROUND MILForD, BEING AN ACCOUNT OF THE REGION COMPRISED IN SHEET 227 or 1He Map. By T. C. Canrritt, B.Sc., F.G.S., E. E. L. Drxon, B.Se., F.G.8., H. H. Tomas, M-A., Se.D.; F.G.8., and/O,. 1. Jonus, M\A., D.Sc.) PIGS pp wa, 185. 1916. Price 2s. 6d.
N the Magazine for 1915 (p. 171) a notice of the memoir explana- | tory to the sheet east of the present one appeared. The general
character of the geology of the area described in the present memoir
is similar to that in the preceding one, but there are differences, some of which are of special interest.
The Pre-Cambrian rocks of the Haverfordwest region are continued into that of Milford, and are there representative of the same two
groups, the Joluston plutonic series and the Benton volcanic series. |
The latter is rich in soda rocks; the former is suspected to be intrusive into the latter. A pneissose structure occurs in some of the Johnston rocks, and as these are thrust, over Lower Carboniferous rocks which exhibit foliation as the result of the thrust, it might be suspected that the gneissose structure was also produced by that thrust, but the field evidence is against this view, and suggests an earlier period for the production of the gneissose structure. Cambrian sediments of Lingula Flag age are found as in the area to the east, and the general succession of ‘the sedimentary Ordovician rocks in the two regions is similar, and therefore requires no further notice.
An interesting feature i in the area under consideration is the marked development of Ordovician volcanic rocks, one certainly and the other probably of Arenig age. These are the rocks of the Trefgarn
and Skomer volcanic series. The Trefgarn Series is developed about
| ' 1 s 1
Reviews—The South Wales Coalfield, Milford. 275
Roch, and consists of keratophyres and other rocks. The remarkable beds of the Skomer Series were described by Dr. H. H. Thomas in 1911 (Quart. Journ. Geol. Soc., vol. Ixvu, p. 175), but further details dre given in this memoir. They vary from rhyolites to olivine basalts, and are interesting on account of the abundance of rocks rich in soda. ‘hey are best developed in Skomer Island, but their relationship with other rocks is seen on the adjoining mainland, where they are overlain by Upper Llandovery beds, which by a curious coincidence also contain contemporaneous volcanic rocks.
_ Of Silurian rocks, the Lower Llandovery beds are similar to those in the eastern region, but not so well developed. The Upper Llandovery beds contain the above-mentioned volcanic rocks of a basaltic character and showing ‘pillow’ structure. In one locality certain beds may be referable to the T'arannon stage, but in parts of the area, at any rate, there is a marked overstep at the base of the Wenlock.
A full description of the Wenlock—Ludlow succession is given, and it is of importance, inasmuch as these beds have a different facies from that of those of the typical Silurian area, being marked by much arenaceous material and an absence of important limestone bands and of graptolitic shales. The presence of Stricklandinia lirata and Pentamerus globosus in Wenlock strata indicates that these forms must be regarded as facies-fossils and not as zone-fossils.
The Old Red Sandstone strata are found on both sides of Milford Haven, and are in many respects similar to those of the Haverford- west region, being divisible into Lower Old Red Sandstone, consisting of conglomerates, sandstones, and marls, and Upper Old Red Sandstone (the Skrinkle Sandstones), composed of sandstones, marls, and limestones.
The junction of the Lower Old Red Sandstone with the Silurian rocks is seen to the north of the Haven. At St. Ishmael’s and Marloes Bay the base of the Old Red conforms with the top of the Silurian, as seen at the Red Cliff and near Gateholm. ‘‘ There is no reason to think that there is any non-sequence.”’ One might
have hoped that the important Hurypterus remipes fauna would have been discovered here: it may yet be found.
Particularly interesting is the succession of strata at the top of the Upper Devonian rocks. “The Skrinkle Sandstones consist of beds of ‘continental facies’ interbedded with ‘‘ grey sandstones, mudstones, and limestones, with an Upper Devonian fauna (‘marine facies’)’’. So far back as 1868 the late J. W. Salter maintained, on account of the presence of Curtonotus and other fossils at West Angle Bay, that marine beds of Devonian age occurred there (Quart. Journ. Geol. Soc., vol. xix, p. 480). The list of fossils given in the present memoir fully confirms his conclusion. A further account of these important rocks is promised when the Pembroke and Tenby Memoir appears. As these beds are succeeded by Carboniferous rocks of the Cleistopora zone, it would seem that here at last we have the longed-for evidence as to the line of demarcation between the Carboniferous and marine Devonian rocks of Britain, with all the light which it will throw upon the ‘ Devonian question ’.
276 Reviews—The South Wales Coalfield, Milford.
Passing to the Carboniferous rocks, we find the Carboniferous Limestone division also developed on the two sides of Milford Haven. To the north there is a limited development at Goultrop Roads, which is of interest from the point of view of tectonics. On the south side the Lower Limestone Shales ( Cleistopora zone) are succeeded by the Main Limestone, of which the lowest part only (Zaphrentis zone) is developed. The Millstone Grit oversteps the underlying rocks. As in the Haverfordwest area, it is separable into three divisions.
The Coal-measures have a thickness of about 6,200 feet. The coals are anthracitic. At the time of the recent survey only one small windlass pit was at work, and the coal industry in the district seems ‘‘to have reached its zenith about the latter half of the eighteenth century’’. The fossil floras indicate that the Coal-measures here belong to the Middle ( Westphalian) division.
A very interesting chapter treats of the Tectonics. One set of movements with lines of Caledonian trend is dominant in the north of the region, and affects rocks up to and including the Silurian strata, though movements occurring after the formation of the Lower Old Red Sandstone, and probably in the interval between its deposit and that of the Upper Old Red, have lines of Armorican trend, due possibly to pressure against a Pre-Cambrian ridge. ‘The Post-Carboniferous movements are dominant in the south. Some lines have a Caledonian direction, but the principal have an Armorican trend.
Details are given of the interesting structures developed by the various movements. The most striking feature is the overthrust of Pre-Cambrian rocks over Carboniferous Limestone as seen in Goultrop Roads, accompanied, as before stated, by schistosity in the later rocks. This limestone had been observed by De la Beche before the middle of the last century. An excellent photograph of the section is given in plate iv of the present memoir.
The superficial deposits are described in. ch. xiv. The South Welsh raised beach has been detected on Milford Haven and in Skokholm Island. As in the area to the east, there is evidence that the ice came from the north-west. Several far-travelled boulders, many apparently of Scottish origin, are found in the drifts. These drifts indicate that the glaciation extended to the south of Milford Haven. In Druidston Haven the Boulder-clay contains marine shells, some of which are characteristically Arctic.
The economic products are described in ch. xv.
The memoir is illustrated by thirty text-figures, maps, etc., and seven plates reproduced from photographs. The maps will be of special use at present, as the colour-printed 1 inch map of which the memoir is descriptive is not yet published. |
To the general geologist the district is perhaps even more interesting than that to the east, and the Skomer yolcanic rocks, the marine Devonian sediments of Milford Haven, and the overthrust of Pre- Cambrian over Carboniferous rocks in Goultrop Roads are especially noteworthy. Furthermore, as will be seen from an inspection of the
photographs, the coast scenery is of a very high character, and those ~
who love to combine study of geology with appreciation of scenery will not regret a visit to the district. To make this successful it will
Reviews—Mesozoic and Cenozoic Echinodermata. 277
be necessary that they should go there with the memoir in pocket as a guide. Jee
Il.—Tuaer Masozorc anp Cenozoic EcurnopErMATA OF THE UNITED Srates. By W. B. Crarx and M. W. Twircuett. Washington, U.S. Geological Survey, vol. liv, 1915. 4to. pp.-8401, with 108 plates. .
‘W\HE marine Mesozoic fauna of North America has hitherto lacked
detailed description in many directions. This is in part due to the relatively poor development of marine deposits of that stage
(and in particular of the Jurassic), and in part to the consequent
superior interest attaching to the Palzozoic and Land Vertebrate
faunas. ‘The volume under review gathers under one cover the
_ results of various more or less incidental investigations upon the Post-
Paleozoic Echinoderms of the United States and adds very materially
to the number of the described species.
All the orders of Echinoderms whose remains are known from the Secondary and Tertiary stages receive attention, but there are not many forms described other than Echinoids, and that order alone seems to provide types of special interest.' In passing, one might protest against the application of a specific name to such obscure casts as those figured under the title of Aspidura idahoensis from the Lower Trias. That the five-rayed markings on the rock do represent Asteroids seems certain, but the fortunate discoverer of a perfect specimen would be totally unable to compare it with the type of this ‘ species’.
The proportionate numerical strength of the Echinoid faunas of the country can be gauged by the fact that 6 pages suffice for the Triassic and Jurassic species, while 55 are required for the Cretaceous and 113 for the Tertiary. In point of preservation and interest, this numerical index is equally reliable. The two Triassic species, both Cidaroids and both new, are represented by small fragments of the test. Of the eight named Jurassic forms, six are Regular Echinoids, of a strikingly European facies, and two might be anything. They are referred to Holectypus, and are as likely to represent that as any other organism, but to give specific names to such material as is figured i is to ‘court confusion. Cidaris taylorensis, a new species from the Lower Jurassic, seems, to judge from the figure, very problematical. Hither it is a Zetracidaris, or some large- tubercled Diademoid. At any rate, the figure does not, as the authors state, show two contiguous plates of the same series,
The Cretaceous Echinoids, and particularly the Regular forms, have a surprisingly European, one might almost say British, character, nearly all the genera being common to the two ‘countries, and the species showing no special differences from those with which European Echinologists are familiar. The Irregular forms are mostly of a littoral type, and compare equally elosely with similar faunas on this side of the Atlantic. The wonderfully prolific stock of the Hemiasters seems to have had a flourishing colony in America, but some, at least, of the species referred to that genus cannot possibly be retained in it.
278 Reviews—Ries and Watson—Hngineering Geology.
The Kocene fauna offers a contrast from the Mediterranean type in the extreme development of the Scutellide and the scarcity of the Clypeastride. In the Oligocene Scutellids and Laganids are still predominant, but a magnificent species of Amblypygus deserves mention. In this section a double systematic disaster has to be recorded. A fragmentary Cidaroid radiole is given a new ‘ specific’ name, and that name is Cidaris smithi. Apart from the fact that - such a specimen does not deserve to be the type of a species, nor even the original of a figure, the name employed is thoroughly preoccupied. Systematists who describe new species of Cidaris (and, alas! their number is still legion) should really be careful about the names they employ. If the patronymic of Smith had been omitted from the thousand or more of names that have followed the word Cidaris, there would indeed have been a marvel to record.
The Miocene and succeeding Echinoid faunas are dominated throughout by the abundance and variety of the ‘Sand-dollars’, and have in all respects a typically American facies.
The volume as a whole is of uniform value, and the plates, though irregular in quality, are lavish and satisfactory. But it is necessary to protest once more against the view that every specimen must have a name, and, if it is too imperfect to be identified with an established species, a new name. Moreover, the descriptions of the species, though admirably concise and intelligible, are almost devoid of references to allied forms. Comparisons, though often to be deprecated, are the most fruitful means of study in the case of a largely new and isolated fauna such as the authors have before them. As an outstanding example of this defect, it may be mentioned that the only new genus instituted is ushered in with no more ceremony than the old ones, and, save for the etymology of its name and the place in the book where it appears, there is no clear indication of the reasons for its establishment nor of its taxonomic position. Excessive brevity is a rare, but irreparable, fault. By tedious filtration the facts may be separated from a prolix account, but no amount of study will extract them from a brief paragraph into which they were never inserted.
Apart from these details, the book affords a useful summary of the present knowledge of the faunas described, and will greatly assist in further work upon them. Its most original feature occurs on the last plate, where a photograph of the scenery on a ranch in California is given to show the abundance and excellent preservation of the Miocene Scutellide. Surely it is to California that all good Echinologists go, when they leave these fields of labour for the Elysian ranches.
We) Ta ee
III.—Ewneinerrineg Grotocy. By Herricw Riss and Tomas L. Watson. Second edition. London, Chapman & Hall, Ltd.; New York, J. Wiley & Sons, Inc. 1915. Price 17s.
N engineer who is at the same time a trained field geologist has a tremendous pull over his colleague whose knowledge in this respect is small. In many engineering courses geology has not been
Reviews—Ries and Watson—Engineering Geology. 279
given the prominent place it should occupy, and many a failure must be attributed to this defect; yet it is hardly possible, or indeed - necessary, for the average student to be as thoroughly grounded in the subject as the geological expert. How much, or how little, stratigraphical geology is necessary is perhaps a question. More is necessary for the mining than the civil engineer, but in any case enough facts should be known to recognize when the expert should be consulted. In the book under review the authors have succeeded well in selecting and discussing those geological principles and topics which have a special bearing upon civil engineering, and in most cases have been able to illustrate their points by reference to actual occurrences in the United States.
In the first part of the book, which deals with rocks and rock- forming minerals, the igneous rocks are classified chiefly by their mega- scopic and microscopic characters, chemical relations being indicated only by silica percentages. A simpler and clearer classification would have been one in which the hypabyssal are separated from the plutonic rocks, on the lines followed by Harker. ‘he classification taken from Kemp is far too complex, and more suitable to the requirements of a petrologist than an engineer.
A valuable chapter is that devoted to underground waters, which will be read with equal advantage by both geologists and engineers. The excellent water-supply papers of the United States Geological Survey have been freely drawn upon, and the results of much detailed work are here assembled in concise form applicable to this country as well as the States. Landslides, which are often of mere academic interest to the geologist, bulk largely in the eyes of the engineer, and receive adequate treatment. A useful table is given.of the slopes that should be adopted in cuts of different depths to avoid sliding. In chapter viii problems of harbour and _ river-mouth improvement are discussed and many cases cited in illustration.
In describing glacial deposits it is shown how necessary it is that the drifts should be mapped, and records of their varying thicknesses and composition recorded whenever possible, if only from the financial point of view. The problem of dealing with glaciers actively interfering with railroad construction does not arise in the , British Isles. In one case, where the Allen Glacier was found to project across the Copper River Valley in Alaska, the engineers blasted out a grade across 54 miles of stagnant, moraine-veneered, tree-covered ice. Ice lies beneath the ties, and future melting or advance will cause trouble and repeated repairs.
Building-stones, limes, cements, clay, and road materials are next described. The importance of testing the durability of a stone is emphasized, although this quality is often relegated to the back- ground. Too.much importance can be attached to crushing strength, for in practically no case is a block of stone required to support a weight approaching anywhere near its limit of strength. It is stated that the use of basalt as a building-stone is not widespread ; we may recall that it has been used with some success in this country as a facing for sea-walls.
Coal, petroleum, natural gas, and ore-deposits also receive adequate
280 Reviews—Fawna of the Batesville Sandstone.
treatment. In the case of coal the theory is proposed that the various stages between plant beds and anthracite are due to a com- bination of an increasing amount of pressure and the heat developed by the pressure, but this theory—as pointed out by the authors— cannot be said to be universally accepted. In this country, for example, it has been shown that the anthracites of South Wales are mainly due to original differences in composition and bear little relation to the earth-movements that have given the coalfield its structure."
In the concluding chapter, on Historical Geology, we have a concise account of North American stratigraphy.
One of the chief defects of an otherwise admirable book is the small space allotted to geological mapsand sections. Lack of detailed knowledge of stratigraphy we can understand, but a civil engineer should be able to interpret nearly every geological map set before him, and this would be almost impossible if he had to rely upon the scant details presented in some five pages of text. As regards geological sections, some of the authors’ are badly drawn, such as figs. 97 and 98, whilst the section, fig. 116, is impossible.
demahs 5
IV.—Fauna or tHe BaresvitteE Sanpsrone or NortHEeRN ARKANSAS. By Grorce H. Grety. Bulletin 593, Department of the Interior, United States Geological Survey (George Otis Smith, Director), 1915. pp. 170, pls. i—x1.
‘{\HIS is a companion work to that on the ‘‘ Wewoka Formation ”’,
issued by the author a few months since, which was noticed in the Gzorogican Magazine for 1915, p. 569, and deals similarly with Carboniferous invertebrates. The Batesville Sandstone is con- sidered to favour a correlation with the Cypress Sandstone and the Ste. Genevieve Limestone, which belong to the later Mississippi Series of the older Carboniferous formation. The fauna is characterized by an abundance of Cephalopoda, large Pelecypods, comparatively few Brachiopoda, besidesmany Bryozoa. In all 128 species are described and. mostly figured, as against 30 species discussed from the same beds by Professor Weller in 1898 (Trans. New York Acad. Sci., vol. xvi). These species are represented under the following groups and genera:—Foraminifera: Zrochammina, Endothyra. Coelenterata: Zaphrentis. Helmintha: Spirorbis. Bryozoa: Batostomelia, Lioclema, Tabulipora, Cystodictya, Glyptopora, Fenestella, Polypora, Archimedes, Rhopalonaria. Brachiopoda: Lingulidiscina, Cranta, Schuchertella, Orthotetes, Productella, Productus, Diaphragmus, Camarotechia, Dielasma, Girtyella, Spirifer, Reticularia, Spirvferina, Clyothyridinia, Composita, Eumetria. .Pelecypoda: Sphenotus, Edmondia, Nucula, Leda, Yoidia, Sulcatipinna, Leptodesma, Cono- cardium, Caneyella, Myalina, Schizodus, Deltopecten, Myoconcha, Lithophagus, Allorisma, Oypricardella. Scaphopoda: Levidentalium. Gastropoda: Lepetopsis, Pleurotomaria, Euconospira, Bembexia(?),
1 Coals of South Wales (Mem. Geol. Surv.), 1908; 2nd ed., 1915.
Reviews—Glacial Geology of North America. 281
Bellerophon, Patellostium, Bucanopsis, Euphemus, Euomphalus, Nati- copsis, Platyceras, Strophostylus, Loxzonema. Cephalopoda: Ortho- ceras, Protocycloceras, Solenocheilus, Goniatites, Gastrioceras, Adelpho- ceras, Aptychus. Trilobita: Griffithides. Ostracoda: Puraparchites, Primitia, Glyptopleura, Cytherelila.
Exception must be taken to two of the above generic determinations. The shell figured and described as Pleurotomaria arkansana might more accurately be referred to Murchisonia, while Pleurotomaria aff. perhumerosa in all probability belongs to Scalites of Emmons as interpreted by De Koninck and other paleontologists of Europe, which according to Eastman (Zittel’s Text-book of Paleontology, 1918, p- 527) should be grouped in the Raphistomide of Ulrich and Scofield, a family with Euomphaloid and Pleurotomaroid affinities.
Ree BON:
V.—Guacrat Groroey or Nort America. PONDEROUS but interesting tome of 529 quarto pages, The Pleistocene of Indiana and Michigan, and the History of the Great Lakes, by F. Leverett and F. B. Taylor, forms Monograph 53 of the United States Geological Survey. It describes the glacial features of a district lying between the areas covered by the previous Monographs Nos. 38 and 41, and presents the latest and most detailed account of the vicissitudes of the immense glacial lakes whose shrunken remnants form even now the greatest system of fresh-water lakes in the world. Four great ice-advances from different directions are now recognized, with three well-marked interglacial stages, and many minor advances and retreats occurred within each stage. Each has left easily traceable topographic effects or deposits; but it is the last, or Wisconsin, stage of glaciation, whose deposits cover practically all the rest, which has modelled the present relief and drainage of the vast area surrounding the Great Lakes. The fluctuations of the ice border have left well-marked morainic systems, each of which is traced ‘across country and fully described in the memoir.
The basins of the Great Lakes were once valleys with free drainage but no lakes. The drainage was obstructed by the ice-sheet in the way with which we are now familiar, thus initiating enormous lakes, ‘the levels and margins of which fluctuated with the movements of the ice. Fortunately they left excellent beaches and unquestionable overflow channels, whereby their former extent and respective outlets have been easily determined. The broad lines of this history are now well known, but with every addition of new facts there is a sensible modification of their details. It has been found especially that the succession of changes involved in the later lake history is much more complex than formerly supposed. This monograph is printed and published regardless of expense, with a beauty and wealth of
illustration that we can only sigh for on this side of the Atlantic.
GW ok:
VI. Bortnes in tHe Terrrarres oF Vicrorta, Austratta.—The ‘“Cainozoic Geology of the Mallee and other Victorian Bores’”’ (Records Geol. Surv. Victoria, iii (4), 1916, pp. 327-430, pls. Lxiii— Ixxvill, price 1s. 6d.), by Frederick Chapman, is a report we have
\ \
282 — Brief Notices.
awaited with some interest. It is a report that necessitated and has received great care and much laborious and tedious work. The material came from eleven borings in the Mallee district, starting 6 miles from the South Australian boundary and penetrating some 20-30 miles or more in a direct east line into Victoria. The first ten were sunk from 200 to 400 feet and the last one to 600 feet, for the special benefit of Mr. Chapman’s report. Water was met with at 170-250 feet from the surface and has risen from 10 to 70 feet in the borings. Full details of each boring are given, and the results of the fauna met with are appended. ‘lhe report should set at rest the vexed question of the age of these Tertiary deposits, for no trace of a Nummulite was found. The paper is illustrated by Mr. Chapman’s rough but characteristic sketches of the microzoa, by photographs of the mollusca, and four sections of rock. We venture to suggest that the plates would have been improved if printed numerals had been cut up and affixed to the prepared plates, instead of their being inserted with the pen.
VII.—Brizr Novices.
1. Yorxksurre’s Conrrisurions to ScleNcE: witad A BrsLioGRaPHY oF Narorat Hisrory Pustications. By T. Suepparp. 8y0; pp. 223. London, 1916. Price 5s. net.
‘{\HIS is a carefully compiled account of the Academies and periodical publications belonging to Yorkshire, to which are
added notes on other publications which contain matter relative
to the county. It forms a sort of supplementary volume to
Mr. Sheppard’s recently published Bibliography of Yorkshire
Geology (Proc. Yorkshire Geol. Soc.). We hope the labour expended
will have its reward in a full appreciation by all Yorkshire geologists
and naturalists.
2. An American Carzpontrerous Fauna.1.—The fauna of the Morrow Group occurring in Oklahoma and Arkansas is critically considered by Mr. Mather and a large number of new species described. ‘The fauna, which occurs in three limestone lenticles in about 400 feet of rocks, is of importance because the associated fossil plants fix its age as Pottsville, and it shows an interesting com- mingling of Mississippian and Pennsylvanian forms, which are clearly distinguished as the residual and proemial elements in the paper. The fauna is compared with others in the Western States and also with the ‘‘ Bergkalkschichten” of Mjatschkowa and. a similar fauna in Spitzbergen. Finally, it is compared with the Pendleside fauna. Judging from the figures given in the fifteen plates it is not improbably very similar to that of the uppermost beds of the Carboniferous Limestone in Derbyshire and Yorkshire, the zone D?,
3. British Fosstt Insrcrs.2—The Lacoe Collection in the United States National Museum contains some fossil insects collected by
1 Kirtley F. Mather, ‘‘ The Fauna of the Morrow Group of Arkansas and Oklahoma’’: Bull. Sci. Lab. Denison University, vol. xviii, pp. 59-284, December, 1915. .
27, D. A. Cockerell, ‘‘ British Fossil Insects’’: Proc. U.S. Nat. Mus., vol. xlix, pp. 469-99, pls. lx—viii, December, 1915. ;
Brief Notvees. 283
P. B. Brodie from the English Lias and the Oligocene of Gurnet Bay, Isle of Wight. Cockerell describes forty-four new species from this material, bringing the total number of described British fossil insects to 368. It is unfortunate that only a few of the far larger collections ‘from the same localities in the British Museum have been described.
4, Tae Occurrence oF Dinosaurs In BusHmantanp.'—These two papers record the occurrence of an Iguanodont Dinosaur in the infilling of a valley in the gneiss of Bushmanland, and give a descrip- tion of the remains, which are scarcely generically determinable. The importance of the find is that it is the first direct evidence that we have obtained of the conditions of the central part of South Africa between the end of the Trias and Recent times. It is to be hoped that these bones may prove the forerunners of a whole series of land vertebrate faunas filling this great gap.
5. Tue Fens.?—In this little pamphlet Professor McKenny Hughes brings together much information of the Fenland, its origin, the peaty strata which cover it, and the marine alluvial surrounding the Wash. ‘The paleontology of the Turbiferous beds is described, and the Shippea man found in them is shown to agree with the Bronze Age men found in the round barrows.
6. PatmontTotoey In Catirornia.—A series of five papers issued within two months bears witness to the activity of the great school of paleontology which Professor J. C. Merriam has built up in the University of California.
7. PaRapavo caLiFrornicus.— Dr. Miller, in the light of much more abundant material, reviews the interesting bird from Rancho la Brea which he formerly described as a peacock. The new investigation
-suggests that it is in many respects intermediate between the peacock and the turkey, and it is hence referred to the new genus Parapavo.
8. In another paper Miller‘ describes two vultures from the Rancho la Brea asphalt-pits, both new genera.
9. Prorgessor Murrram® describes very fragmentary material from the Etchegoin as Pliohippus proversus. This horse, which is near ‘ Hquus’ simplicidens from the Texan Pliocene, seems to provide an intermediate stage between the typical Pliohippi and such primitive horses as Hguus stenonis.
10. American Brsons.°—The paper contains a detailed discussion, with many measurements, of a fine series of skulls and jaws of Bison
1 A. W. Rogers, “‘ The Occurrence of Dinosaurs in Bushmanland.’’ S. H. Haughton, ‘“‘ On some Dinosaur Remains from Bushmanland’’: Trans. Roy. Soc. S. Africa, vol. v, pt. iii, pp. 259-72.
2 Notes on the Fenland, by T. McKenny Hughes; with ‘‘A Description of the Shippea Man’’, by A. Macalister. Cambridge, University Press, 1916, 6d.
3 L. H. Miller, ‘‘ A Review of the species Pavo californicus’’: Univ. Cal. Bull. Dept. Geol., vol. ix, No. vii, pp. 89-92.
+ L. H. Miller, ‘‘ Two Vulturid Raptors from the Pleistocene of Rancho la Brea ’’: op. cit., No. ix, pp. 105-9.
° J. C. Merriam, ‘‘ Relationship of Hguus to Pliohippus suggested ’ by Characters of a New Species from the Pliocene of California’’: op. cit., No. xviii, pp. 525-34.
5 A.C. Chandler, ‘‘ A Study of the Skull and Dentition of Bison antiquus,
Leidy, with special reference to material from the Pacific Coast’’: op. cit., No. xi, pp. 121-35.
284 Reports & Proceedings—Geological Society of London.
antiquus, an extinct Pleistocene Bison, found throughout the United States, which differs from the living American Bisons with larger horn-cores and differing markedly in their angle of insertion.
11. Catrrorntan Puiocenz.1—The paper is a valuable contribution to the later Tertiary stratigraphy of California, containing as it does descriptions of many sections with very full faunal liste, which are carefully analysed, the percentage of species restricted to a given formation and those ranging through into others being well brought out.
12. Miocenr Verreprates rrom Nevapsa.*—In this paper Professor Merriam describes an important but unfortunately fragmentary fauna of Upper Miocene age from West Nevada, and compares it with other groups of mammals of similar age in the State. The most interesting types are Hypohippus nevadensis, a species with remarkably primitive milk molars representing a new sub-genus Drynohippus, and Tetra- belodon sp., an interesting Mastodon with a symphysis of a length intermediate between typical Tetrabelodons and ordinary Mastodons.
REPORTS AND PROCHEDINGS.-
I.—Gerotocicat Socrery or Lonpon. May 10, 1916.—Dr. Alfred Harker, F.R.S., President in the Chair.
The following communications were read :—
1. ‘‘ Carboniferous Fossils from Siam.” By F. R. Cowper Reed, MAR ScD EGas.
The fossils described in this paper were collected by the Skeat Expedition from Cambridge in the year 1899, at a locality called Kuan Lin Soh, in the Patalung district of Lower Siam, and were briefly mentioned in the ‘Reports’ of the British Association for 1900 and 1901. ‘hey occur in a pale, fine-grained, jointed siliceous rock with an irregular or sub-conchoidal fracture. The field relations of the beds have not been recorded. ‘he general facies of the small fauna which the available material has yielded indicates a Lower Carboniferous age for the beds, and the affinities of the species seem to be European and suggest the Culm Series. In 1913 Mr. J. B. Scrivenor, on the strength of the earlier determination of the fossils,
referred the beds to his Raub Series of the Malay Peninsula, and the _
author draws attention to other Carboniferous beds in South-Kastern Asia.
2. ‘‘The Lurgecombe Mill Lamprophyre and its Inclusions.” By Herbert Gladstone Smith, B.Sc., F.G.S.
A lamprophyre-dyke intrusive into Culm Shales has recently heen exposed at Lurgecombe Mill, near Ashburton (South Devon). The rock is compact and fine- erained, small crystals of biotite
1 Bruce Martin, ‘‘ The Pliocene of Middle and Northern California ’’: op. cit., No. xv, pp. 215-59.
2 J.C. Merriam, ‘‘ Tertiary Vertebrate Fauna from the Ada Mountain Region of Western Nevada ’’: op. cit., No. xili, pp. 161-98. /
(edat
Reports & Proceedings—Geological Society of Glasgow. 285
imparting to it a characteristic lamprophyric appearance; vesicles with secondary minerals appear towards the margins.
In thin section, idiomorphic biotite, olivine pseudomorphs, and felspars are seen to make up the bulk of the rock; chlorite and secondary quartz occupy the interstices.
Analysis yields a small percentage of alkalies, the potash being slightly lower than the soda. -
One of the thin sections was seen to contain crystals of blue corundum associated with magnetite, in a patch which was obviously foreign to the rock. With the object of obtaining additional examples, many slices were cut, sections being made of those that seemed promising. In this way several of these inclusions were obtained, the largest being about 0°3inch in diameter. All contain’ corundum and magnetite, but in some cases staurolite also is present and more rarely green spinel. Further information concerning the corundum and staurolite was obtained by crushing the rock, and separating the constituents by means of heavy liquids. A well-formed crystal of the former mineral is tabular, large basal planes being combined with a subordinate rhombohedron, and it is probable that all the corundum of the rock is tabular in habit.
The corundum, staurolite, green spinel, and associated minerals probably owe their origin to a process of inclusion of fragments of the argillaceous country rock, and very definite borders of biotite surrounding some of the inclusions suggest that these are merely unassimilated remnants of larger fragments.
Il.—Gerotogicat Society ofr Giascow.
1. At a meeting of the Geological Society of Glasgow on April 13 Mr. Alex. McLean read ‘‘ Notes on the Age of the Human Race based on Evidence found in Post-Pliocene Strata”. He referred to the
_opinion held in certain quarters that the age of the human race was not many times greater than the sum of the classical and historical periods, and quoted many authorities to show that, so far from this being the case, the investigations carried out during the last half- century had produced evidence of a vastly greater antiquity. In the ancient river gravels and in caves and on other sites human relics had been found which gave clear evidence of a series of well-marked stages in the progress of the race from a state of extreme simplicity.
Mr. H. R. J. Conacher read ‘‘ Notes on an Occurrence of Petrified Plant Remains in Lower Limestone Strata at Bridge of Weir”. He said that in the strata immediately underlying the Blackhall Lime- stone in the banks of the Gryfe there was exposed a group of about half a dozen tree-stumps. These showed the well-known external characters of the roots of ZLepidodendron and Sigillaria, and in addition parts of the internal woody tissue. The main axis showed that a kind of ‘tap-root’ had existed, and a series of slowly tapering ironstone cylinders, with calcite cores, which penetrate the embedding shale, no doubt represent the rootlets proceeding from the spreading roots. So far none of these rootlets have been found with any vestiges of internal structure preserved, but such may yet come to
286 Reports & Proceedings—Liverpool Geological Society.
light. Relics of aerial branches also occur, but these are in a state of preservation much less favourable for microscopic study. ‘The tissues in the main roots where in the best condition have been preserved in calcareous material, which permits the employment of high powers of magnification, and the structures are undeformed by pressure, but the aerial stems are preserved in iron pyrites, the opaque crystals of which have quite obliterated the finer details. It would seem that the roots, embedded in the soft mud and readily accessible to the petrifying mineral solutions, had thus had their harder parts preserved from decay and enabled to resist the pressure exerted by the overlying deposits. The aerial branches, on the other hand, shaken from the dead trees were already much decayed and deformed by pressure before the mineral solutions had the opportunity to act. A series of specimens from the locality was exhibited, including microscope sections shown by the aid of the micro-proj ector.
I1J.—Liverroot Geronocicat Society.
April 11, 1916.—J. H. Milton, Esq., F.G.8., F.L.S., President, in the Chair.
The following paper was read :—
‘‘ Notes on some Ferruginous Nodules in the Panna Triassic Sand- stones of South-West Lancashire.” By T. A. Jones.
The author first described some small hard spheroidal concretions found last year during trench digging at Knowsley Park, presumably in Lower Soft Bunter Sandstone. They consisted of sand-grains embedded in a dark-brown cement of hydrated ferric oxide, which in volume was at least equal to the detrital material. The cores of the concretions were lighter in colour and less perfectly cemented than the outer shell. A striking feature was the large quantity of secondary silica present.
The so-called ‘sulphur-balls’ found in large numbers in colliery borings at Wigan and St. Helens in soft sandstone overlying the Coal- measures were then described. These consist of well-rounded grains of quartz and quartzite cemented by iron pyrites or marcasite. The most interesting and significant feature characterizing them is the presence of small knots of grains cemented by calcite. Tiny fragments of calcite also occur attached to the detrital grains, or le isolated in the ferric sulphide. A gradual replacement of an earlier calcareous cement by ferric sulphide has therefore taken place, and this without disturbing the stratification of the sand-grains which is clearly visible across the nodules. A _ brief discussion of the origin of the iron cementing material in the sandstones followed.
CORRESPON DEHN CEH.
THOUSAND FOOT PLATFORM IN ARRAN. Sir,—Dr. F. Mort, in his paper on ‘‘ Glacial Erosion in N. Arran” (abstract Trans. Geol. Soc. Glas., vol. xv, p. 415), calls attention to
a
Obituary—Lreut. R. L. Valentine. 287
a ‘platform’ at 1,000 feet above sea-level. In my paper on the Arran Granite (Trans. Geol. Soc. Glas., vol. x, p. 216) I notice the immense denudation that had taken place in Arran when the sea worked at 600 to 1,300 feet above present sea-level, and give sections. I also note the fact that all the glens (with one notable exception) occur in synclines of the granite slabs, and all the mountains have the slabs arranged as anticlines or quaquaversal dips (with one exception). J have also shown by a diagram that the slabs dip all round the granite area (which is nearly circular) at from 15° to 45° towards the slate, and give what I consider to be an explanation of these features. I also note the principal glacial phenomena, the thickness and quality of the Boulder Drift, moraines, etc., and how the drift had been carried all round the granite area on to the slate. I may say here that I saw no boulders foreign to the island on the granitic area, which is about 41 square miles. I do not, of course, suppose that all the immense denudation noted above took place during the Glacial Period—probably only a very small part of it. It is my firm opinion that the slate partly filled what are now the valleys at one time, and being more easily denuded than the granite this gave the original direction to the valleys or glens. In other papers I have shown that there is no Arran Granite in Ayrshire, except small bits along the shore which may have been brought as ballast. J. Smiru. DYKES, DALRY, AYRSHIRE. May 6, 1916.
OHS er ASevae
PeUe Re bo VALENTINE: 7tH Battarion Royat Dusiin Fusiniers, GEOLOGIST ON THE GroLocicaL SurvEY or IRELAND.
BoRN APRIL 16, 1890. DIED APRIL 30, 1916.
Lizvr. R. L. Vatenrine, of the 7th Battalion Royal Dublin Fusiliers, who died from wounds in France on April 30, 1916, was born on April 16, 1890, at Portora School, near Enniskillen, where his father was classical master. He was educated at the High School, Dublin, and gained a scholarship in the Royal College of Science for Ireland, receiving the Associateship of the College in 1912. He especially devoted himself to natural history and geology, and was engaged on a research in 1913-14 as to the horizon of the lowest Avonian strata at Hook Head, co. Wexford. He obtained by competition the post of Geologist on the Geological Survey of Ireland, and completed the Civil Service qualifying examination while in military training at the _ outbreak of the War. He gave high promise of becoming prominent amongst scientific men in Ireland, and his unfailing cheerfulness and readiness of resource endeared him to those who looked forward to working with him as a colleague. Gis J..C.
288 Miscellaneous.
MISCHITMAN HOUS.
GroLocicaL Notres or QuEENSLAND.!
From the Gulf of Carpentaria to the Darling Downs, north to south, the fossil remains of extinct mammalia have been found in indurated muds, the beds of old watercourses. The bones and teeth are those of Diprotodon Australis, Macropus titan, Thylacoleo, Phascolomys, Nototherium, crocodile teeth, etc. The Dzprotodon inhabited the Queensland valleys abundantly, and the Crocodilus Australis had a great range inland. he Diprotodon remains are found chiefly in the most permanent water-holes. No human bones, flint flakes, or any kind of native weapons have yet been discovered with the extinct mammalia of Queensland.
Desert sandstone is the most recent widely-spread stratified deposit developed in Queensland. Since it became dry land the denudation of this formation has been excessive, but there is still a large tract in situ. Probably this desert sandstone covered the whole of Australia at one time. (It is possible that desert sandstone in Queensland has value for free gold.) On the vast plains west of the dividing range Cretaceous strata are found; hot alkaline springs occur in these plains, and the discovery of these suggested the possibility of the existence of artesian water long before the bores were sunk from which flow ‘‘ Queensland’s rivers of gold”’.
The whole of Queensland is a vast cemetery of fossilized species— on the surface, buried in drifts, or hidden in clays. The plains of the Flinders River disclose great deposits of marine fossil shells— Belemnites and Ammonites and remains of extinct animals. In the Gulf of Carpentaria, 40 or 50 feet below the alluvial deposits forming the banks of rivers, firmly embedded in the hard cement—water- worn stones in an ironstone clay—are the bones of innumerable extinct gigantic animals that, far back in prehistoric ages, roamed over the Gulf country: Diprotodon, Nototherium, Zygomaturus, and Thylacoleo, grass-eaters and flesh-eaters. The utter extinction of these creatures can only be explained by a great change of climate and prolonged periods of drought. Gigantic alligators, turtles, and marsupials abounded in those days, suggesting a luxuriant and abundant vegetation, both trees and herbage.
From an economic point of view one may say that three-fourths of the area of Queensland forms good pastoral land. Of this 60,000 square miles contain valuable mines of gold, with outcrops of copper and lead ores, as well as rich deposits of tin; 24,000 square miles are capable of producing illimitable supplies of iron and coal. It may be safely asserted that in Queensland is a wealth of material resource comparing favourably with any other part of Australia.
1 From the London Correspondent of the North Queensland Register, 22 Basinghall Street, London, E.C.
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NEW SERIES. DECADE VI. ee, Institys No. VIL—JULY, 1916 =.{ jy) 19 1916
ORIGINAL ARTICLES. Nag; oh oe a l0na| WiUSoS
I.—Eminent Livine Gerotoaists.
Joan Epwarp Marr, Sc.D. (Camb.), F.R.S., F.G.8., Fellow and Lecturer of St. John’s College, Cambridge, and University Lecturer in Geology.
(WITH A PORTRAIT, PLATE XI.)
fJ\HE subject of the present memoir occupies a distinguished
position as lecturer and teacher of our science in the University of Cambridge, one which he has held for more than thirty years, and he is well known among geologists generally as a high authority on the Paleozoic rocks, his writings being recorded in the “Quarterly Journal’”’ of the Geological Society (of which Society he has filled the offices both of Secretary and President). His name has also frequently appeared as the author of important papers in the Gronoeicat Macazrnx and other works.
John Edward Marr, the third son of John and Mary Marr, was born at Morecambe, Lancashire, June 14, 1857; he was educated at the Lancaster Grammar School, already famous as having been the nursery of two eminent scientific men, Dr. Wm. Whewell, F.R.S., Master of Trinity, and Professor Sir Richard Owen, K.C.B., F.R. g.. Hunterian Professor at the Royal College of Surgeons and afterwards head of the Natural History Departments i in the British Museum.
For some years before entering Cambridge, Marr lived at Carnarvon, where his interest in geology was aroused among the rocks of Snowdonia, and when at school he had the advantage of geological teaching from the Rev. Thomas Adams, M.A., and practical work in the field under Mr. R. H. Tiddeman, M.A., F.G.S., who was then surveying the Lancaster district.
In 1875 J. EK. Marr entered St. John’s College, Cambridge, with an Exhibition, and had the benefit of studying under Professor McKenny Hughes and the Rev. T. G. Bonney, in the lecture-room, museum, and field. By his application Marr obtained a Foundation Scholarship, and graduated First Class in the Natural Science Tripos in 1878.
The year following he spent some weeks in a careful study of the Lower Paleozoic rocks of Bohemia and critically examined Barrande’s so-called ‘colonies’, of which that accomplished geologist had published so much. The writer recalls the humorous remark of Professor Huxley at a Council meeting of the Geological Society, that now Marr had upset Barrande’s interpretation of these isolated
DECADE VI.—VOL. III.—NO. VII. 19
290 Hminent Living Geologists—Dr. J. EH. Marr.
masses he should, alas! receive no more pamphlets from Prague on the ‘‘ Defense du Colonies’’, which were so entertaining.
In 1880 Marr spent a considerable time in visiting the historical localities of the Lower Paleozoic rocks of Scandinavia. Both these expeditions were aided by grants from the Worts Travelling Fund of the University. The results of his investigations were presented in papers read before the Geological Society and printed in the Quarterly Journal and the Gronoercan Magazine (1881, p. 245; 1882, p. 282; 1883, p. 263, etc.). |
During this period Marr had the advantage of much useful training in lecture-work while acting as Lecturer to the University Extension, Scheme, and for one winter of that period he served the office of Deputy to Professor A. H. Green at Leeds.
J. E. Marr was elected a Fellow of St. John’s College, Cambridge, in 1881, and appointed University Lecturer in Geology in 1886, having been informally engaged in teaching in the University some years previously. Shortly after his appointment he was also made College Lecturer in Geology.
Since 1886 Dr. Marr has devoted himself mainly to teaching in Cambridge and to geological research. His studies in the field were largely in the complex Paleozoic rocks of the Lake District, but embraced other home areas, as well as on the Continent. He has done much work as an Examiner at Cambridge and other Universities and has served on many Boards and Syndicatesin the University, and has been elected to the Councils of the Royal Society, the British Association, and the Geological Society. He entered the Council of the last-named Society in 1885, and has since served almost continuously, save for five years in a period of thirty-one, filling the office of Secretary for ten years, Vice-President during sixteen years, and as President for two years.
In carrying out field-work he has been fortunate in his colleagues, including, among others, Thomas Roberts, Alfred Harker, Henry Alleyne Nicholson, and E. J. Garwood. One of the heavy blows in his life was the loss of Nicholson at a time when his friends all hoped that he had many years of good work before him.
Dr. Marr writes: ‘“‘The geologist goes into the field not only as a researcher, but ever as a student, and in these later years I grate- fully recall the instruction I have received from Professor Charles Lapworth, at whose feet so many geologists have sat.” He also acknowledges to have received much assistance from many of his pupils while carrying on field observations. He was being helped in the Lake District by his son (now Captain Alleyne Marr) when the War broke out; Captain Marr is now serving at the Front.
Owing to the almost continuous service of Dr. Marr as a Member of Council, it was difficult to find an occasion when that body could vote one of its medals to a Fellow who, by his long-continued services, had done so much to aid the science of geology and the interests of the Society. It came in 1900, when he was awarded the Lyell Medal, and the President referred to his numerous contributions to the Society’s Journal and to the Grotoeican Magazine (from 1876 onwards) on the Lake District and its borders,
a
Eminent Living Geologists—Dr. J. HE. Marr. 291
on Wales, and on the pre-Devonian rocks of Bohemia. He also specially referred to those on the Stockdale Shales (in conjunction with the late Professor Nicholson), on the Shap Granite and its associated rocks with Dr. Alfred Harker, F.R.S. (the present President), and on limestone knolls. Mr. Whitaker also cited other works by Dr. Marr on The Cambrian and Silurian Rocks, The Principles of Stratigraphical Geology, and The Scientific Study of Scenery.
Fourteen years later (in 1914) the Council awarded the blue ribbon of the Geological Society, the Wollaston Medal, to Dr. Marr, and the President, Dr. Aubrey Strahan, referred to his brilliant University career and the continuity of his labours since 1880 in the task of assisting the Woodwardian Professor to create in Cambridge the foremost school of geology in Britain. He described Dr. Marv’s investigations in the field on the Lower Paleozoic rocks and on the zoning of the strata between the Coniston Limestone and the Coniston Grits in the Lake District, on the continuation of those researches into North Wales, and the comparison of the sequence, as there developed, with that of the Lake District. He referred to Marr’s visit to Bohemia and his investigation of the boundary between the Cambrian and Silurian, and his careful comparisons of the Bohemian and British developments, incidentally to show that there existed serious objections to the acceptance of Barrande’s colonies, both on paleontological and stratigraphical grounds.
No sketch of his life-labours in Cambridge would be complete if we failed to pay a tribute to the able way in which Dr. Marr’s teaching work has been aided and encouraged by his wife. One of his old students writes: ‘‘Marr’s profound knowledge of his subject, his youthful enthusiasm, and his sympathy with the undergraduate have all contributed to make him the most successful of teachers. It has always been his endeavour to get into closer touch with his pupils than could well be done in the lecture-room, and in this he has been aided in no small measure by his wife. Every Sunday afternoon and evening during term-time students were welcomed at their house, a privilege and a kindness that meant much to the undergraduate, who sees all too little of home-life while at the University. Neither Marr nor Mrs. Marr lose sight of a student when he leaves Cambridge, for by that time he has passed from the status of pupil to that of personal friend, and his advance in the geological world is aided and watched with pleasure.”
The following are the principal dates relating to Dr. Marr’s career: B.A. 1879; M.A.1882; Se.D.1904; F.G.S.1879; F.R.S. 1891; Sec. G.S. 1888-98 ; V.P.G.S. 1901-3, 1906-8, 1911-13; Pres. G.S. 1904-6; Lyell Medallist 1900 ; Wollaston Medallist 1914.
Dr. Marr received Hon. Ph.D. in the Bohemian University of Prague in 1908; President Section C (Geology) British Association 1896; delivered lecture to Operative Classes at Cambridge Meeting of British Association 1904 ; delivered Tyndall Lecture at Royal Institution 1906.
He is an Honorary Member of the Geologists Association and of other British
Scientific Societies ; also of the Geological Society of Belgium, and the Natural History Society of New Brunswick.
Dr. Marr is the author of the following publications :—
1878.
1880.
1881.
1882.
1883. 1885.
1887.
1888.
1889.
1890.
1891.
Eminent Inving Geologists—Dr. J. HK. Marr.
. ““ Note on the Occurrence of Phosphatised Carbonate of Lime at Cave Ha,
Yorkshire’’: GEOL. MAG., Dec. II, Vol. III, pp. 268-9.
** Fossiliferous Cambrian Shales near Caernarvon ”’ : Quart. Journ. Geol. Soc., vol. xxxii, pp. 134-5; Phil. Mag., ser. Vv, vol. i, p. 329.
‘“On some well- defined Life-zones in the lower part of the Silurian (Sedgw.) of the Lake District ’’: Quart. Journ. Geol. Soc., vol. xxxiv, pp. 871-85.
‘“ Note on the Phacopide of the Lake District’’: Proc. Camb. Phil.
: Soc., vol. iii, pp. 68-9.
‘“ On the Cambrian (Sedgw.) and Silurian Beds of the Dee Valley, as compared with those of the Lake District’ (1879): Quart. Journ. Geol. Soc., vol. xxxvi, pp. 277-84.
“* On the Predevonian Rocks of Bohemia’’: Quart. Journ. Geol. Soc., vol. xxxvi, pp. 591-618.
““ Syllabus of a Course of Lectures on Geology’’: Cambridge University Local Lectures, pp. 31.
‘“On some Sections in the Lower Paleozoic Rocks of the Craven District’’: Proc. Yorks Geol. Soc., vol. vii (1878-81), pp. 397-9. “The Classification of the Cambrian and Silurian Rocks’’?: GEOL.
MAG., Dec. II, Vol. VIII, pp. 245-50.
The Classification of the Cambrian and Silurian Rocks. Being the Sedgwick Prize Essay for 1882, pp. xxiv, 147.
‘* On the Cambrian (Sedew.) and Silurian Rocks of Scandinavia”? : Quart. Journ. Geol. Soc., vol. xxxviii, pp. 313-27.
*“ Origin of the Archewan Rocks’’: Grou. MaaG., Dec. II, Vol. X, pp. 263-73.
(With T. Roperts) ‘‘ The Lower Paleozoic Rocks of the Neighbourhood of Haverfordwest’? : Quart. Journ. Geol. Soc., vol. xli, pp. 476-91, 1 map.
“* The Lower Paleozoic Rocks near Settle’’: Grou. MaG., Dec. III, Vol. IV, pp. 35-8.
** On the Lower Paleozoic Rocks of Settle’’: Rep. Brit. Assoc., 1886, pp. 663-4.
‘“ The Work of Ice Sheets’’: GHOL. MAG., Dec. III, Vol. IV, pp. 151-5.
“‘ The Glacial Deposits of Sudbury, Suffolk’’: Grou. MAG., Dec. IL, Vol. IV, pp. 430-1.
““ On Homotaxis’’: Proc. Camb. Phil. Soc., vol. vi, pp, 74-82.
‘* Some Effects of Pressure on the Sedimentary Rocks of North Devon ”’ : Rep. Brit. Assoc., 1887, p. 706; Grou. MaG., Dec. III, Vol. V, pp. 218-21.
(With H. A. NicHox~son) ‘‘The Stockdale Shales’’?: Quart. Journ. Geol. Soc., vol. xliv, pp. 654-734.
‘* Qn the Superimposed Drainage of the English Lake District’ : GOL. MAG., Dec. III, Vol. VI, pp. 150-4.
‘* Notes on the Lower Paleozoic Rocks of the Fichtelgebirge, Franken- wald, and Thuringerwald’’: Grou. Mac., Dec. III, Vol. VI, pp. 411-15.
‘* Dynamic Metamorphism of Skiddaw Slates’’: Rep. Brit. Assoc., 1889, p. 568.
‘* The Connection betwixt Yorkshire and Scandinayvia’’: The Naturalist, 1890, p. 145.
‘* The Backbone of England’’: Trans. Leeds Geol. Assoc., pt. vi, p. 51.
‘* Pre-Cambrian, Cambrian, and Silurian’’: Report of British Committee on Classification and Nomenclature ; Compte Rendu Congrés Geol. Intern. (1888), pp. B 161-78.
(With ALFRED HARKER) ‘‘The Shap Granite, and the Associated Igneous and Metamorphic Rocks’’: Quart. Journ. Geol. Soc., vol. xlvii, pp. 266-328.
(With H. A. NicHoxson) ‘‘Cross Fell Inlier’’: Quart. Journ. Geol. Soc., vol. xlvii, pp. 500-12, pl. xvii.
1892.
1893.
1894.
1895.
1896.
1897. 1898.
Eminent Living Geologists—Dr. J. EH. Marr. 298
(With R. H. TippEMAy) ‘‘ The Geology of West Yorkshire ’’ : Compte Rendu Congrés Geol. Intern. (1888), p. 303.
(With H. WoopwarD, R. ETHERIDGE, and G. F. WHIDBORNE) ‘‘ The best methods for the Registration of all Type Specimens of Fossils in the British Isles’’: 1st Rep. of Committee, Brit. Assoc. Rep., 1890, p. 339; 2nd Rep., 1891, pp. 299-300 (1892); 3rd Rep., 1892, p. 289 (1893) ; 4th Rep., 1893, p. 482 (1894).
*“ Geology of Appleby’’: Chapter v of a Guide-book to Appleby, by Canon Mathews, pp. 71-5.
** On the Wenlock and Ludlow Strata of the Lake District’’?: GEOL. MaG., Dec. III, Vol. IX, pp. 534-41.
‘* The Coniston Limestone Series’’: GEOL. MAG., Dec. III, Vol. IX, pp. 97-110.
“Further Remarks on the Coniston Limestone’: GEOL. MAG., Dec. III, Vol. IX, pp. 443-7.
(With ALFRED HARKER) ‘‘ Supplementary Notes on the Metamorphic Rocks around the Shap Granite’’?: Quart. Journ. Geol. Soc., vol. xlix, pp. 359-71, pl. xvii.
‘* Physiographical Studies in Lakeland’’: GEOL. MaG., Dec. IV, Vol. I, pp. 489-539.
** Works on the Paleozoic Rocks, published in 1894’: Sci. Progress, vol. ii, pp. 96-108. ;
(With T. LEIGHTON) ‘‘ Excursion to Cambridge and Ely’’: Proc. Geol. Assoc., vol. xiii, pp. 292-5.
‘** Foreign Work amongst the Older Rocks’’: Sci. Progress, vol. iii, pp. 10-22.
‘* Physiographical Studies in Lakeland ’’: GEOL. MAG., Dec. IV, Vol. II, pp- 299-303.
‘‘ The Tarns of Lakeland’’: Quart. Journ. Geol. Soc., vol. li, pp. 35-48.
‘The Study of the Ancient Sediments’’: Sci. Progress, vol. iv, pp. 1, 313-22.
(With EK. J. Garwoop) ‘‘ Zonal Divisions of the Carboniferous System ”’ : Grou. MaG., Dec. IV, Vol. II, pp. 550-2; Rep. Brit. Assoc., 1895, p. 696.
(With H. A. NicHoxson) ‘‘ Notes on the Phylogeny of the Graptolites’’ : GEOL. MaG., Dec. IV, Vol. II, pp. 529-39.
‘* Forms of Mountains’’: Nat. Sci., vol. vi, pp. 240-3.
(With H. A. NICHOLSON) “Notes on the Phylogeny of the Graptolites’’: Rep. Brit. Assoc., 1895, p. 695.
“ Additional Notes on the Tarns of Takeland 7: Quart. Journ. Geol. Soc., vol. lii, p. 12.
Address to the Geological Section of the British Association: Rep. Brit. Assoc., 1896, vol. lxvi, pp. 762-75 ; Nature, vol. liv, pp. 494-500 ; GEOL. MaG., Dec. IV, Vol. III, p. 464.
‘‘ The Graptolites ’’: Sci. Progress, vol. v, pp. 360-73.
“* On the Lake Basins of Lakeland ’’: Proc. Geol. Assoc., vol. xiv, p. 273.
‘* The Lake Basins of Lakeland ’’ (abstract): Glac. Mag., vol. iv, p. 21.
‘The Waterways of English Lakeland’’ (map, 1 inch = 4 miles): Geog. Journ., vol. vii, pp. 602-25.
‘“* Life-zones in the British Carboniferous Rocks’’: Report of the Committee appointed to study the Life-zones in the British Carboniferous Rocks. Rep. Brit. Assoc., 1895, p. 696; GEOL. MAG., Dec. IV, Vol. III, p. 519.
“The Origin of Lakes’’: Sci. Progress, N.S., vol. i, pp. 218-28.
The Principles of Stratigraphical Geology (Camb. Nat. Sci. Ser.), pp. 304, text-illust.
““The Development of British Scenery ’’: Sci. Progress, vol. vii, pp. 275-86.
(With R. H. Apr) ‘‘ The Lakes of Snowdon’’: Gro. MAG., Dec. IV, Vol. V, pp. 51-61.
1900.
1901.
1902. 1903.
1904.
1905.
1906.
1907.
1909.
1910.
1911.
Eminent Living Geologists—Dr. J. EH. Marr.
. ‘‘Note on a Conglomerate near Malmerby [Cumberland]’’ : Quart. Journ.
Geol. Soc., vol. lv, pp. 11-13, fig.
** On Limestone-knolls in the Craven District of Yorkshire and else- where’’: Quart. Journ. Geol. Soc., vol. lv, pp. 327-8, pl. xxiv ; Abs. Proc. Geol. Soc., 1898-9, pp. 88-9.
The Scientific Study of Scenery, pp. ix, 368, text-iliust.
‘* Notes on the Geology of the English Lake District’’: Proc. Geol. Assoc., vol. xvi, pp. 449-83.
‘* Tiong Excursion to Keswick’’ (with Supplementary Excursion to Causey Foot, Eycott Hill, and Threlkeld Mine, under the leader- ship of John Postlethwaite ; photographs, pl. xiv, by A. K. Coomara- swamy): Proc. Geol. Assoc., vol. xvi, pp. 526-32, pls. xiii, xiv, map (Voleanic Rocks of the Lake District).
‘“ The Origin of Moels and their subsequent Dissection ’’: Rep. Brit. Assoc., 1900, pp. 818-19; Geog. Journ., vol. xvii, pp. 63-9, figs.
[‘‘ Origin of Coal’’]: GEoL. MaG., Dec. IV, Vol. VIII, pp. 33-4.
“* Lakes of Snowdonia ’’: GEOL. MAG., Dec. IV, Vol. IX, pp. 430, 527.
se sas Geology, pp. xi, 318, figs., 1 pl. (geol. map of the British Isles).
‘“The Geology of Cambridgeshire’’: GEOL. MaG., Dec. V, Vol. I, pp. 508-9.
‘* Geology of the Shap District’’: in Rev. J. Whiteside’s Shappe im Bygone Days, pp. 253-72.
(With W. G. FEARNSIDES) The Physiography of Com : Handbook to Nat. Hist. Camb., ed. by J. EH.
(With A. E. SHIPLEY, etc.) Handbook to the Nabiad History of Cambridgeshire, pp. viii, 260, 4 maps (1 geol.).
Anniversary Address (‘‘ The Classification of the Sedimentary Rocks’’) : Abs. Proc. Geol. Soc., 1904-5, pp. 52-3; Quart. Journ. Geol. Soc., vol. lxi, pp. lxi-lxxxvi.
““ The Geology of Cambridgeshire ’’’: Rep. Brit. Assoc., 1904, pp. 541-2.
An Introduction to Geology, pp. viii, 229, 3 pls., text-illust.
Anniversary Address (‘‘ The Influence of the Geological Structure of English Lakeland upon its Present Features—A Study in Physio- graphy ’’) : Abs. Proc. Geol. Soc., 1905-6, pp. 59-60; Quart. Journ. Geol. Soc., vol. lxii, pp. Ixvi-lxxvii, figs., 1 pl.
‘* On the Stratigraphical Relations of the Dufton Shales and Keisley Limestone of the Cross Fell Inlier ’’: Grou. MAG., Dec. V, Vol. III, pp. 481-7, figs. (geol. map).
‘“On the Ashgillian Series’?: Gzonu. Mac., Dec. V, Vol. III,
pp. 59-69.
‘“ The Geology of the Appleby District, Westmorland ’’: Proc. Geol. Assoc., vol. xx, pp. 129-48, figs., pls. i and iii (geol. map), and pp. 193-9, fig., pls. vi, vii.
‘On a Paleolithic Instrument found in situ in the Cambridgeshire Gravel’’?: GEoL. MAG., Dec. V, Vol. VI, pp. 534-7, Pl. XXXI.
(With W. G. FEARNSIDES) “The Howeill Fells and their Topography’’ Abs. Proce. Geol. Soc., 1908-9, p. 120; Quart. Journ. Geol. Sood ; vol. lxv, pp. 587-610, figs., pls. xxvili-xxxi (rivers and glacial
maps). ‘“The Lake District and Neighbourhood: Lower Paleozoic, Upper Paleozoic, and Neozoic Times ’’: Geo]. Assoc., Jubilee Vol., pt. mi,
pp. 624— 60, figs.
(With W. G. FEARNSIDES) “* Notes on the Lower Paleozoic Rocks of the Cautley District, Sedbergh (Yorks)’’ (abstract): GEOL. MAG., Dec. V, Vol. VII, pp. 474-5.
(With A. STURGE, NINA F, LAYARD, F. CORNER, W. WHITAKER, and W. C. UNDERWOOD) Report of the Special Committee on Sub-Crag Implements: Proc. Prehist. Soc. H. Anglia, 1897, vol. i, pp. 93-43, pls. ii—vii.
Florence J. Relf—Some Wealden Sands. 295
(With W. G. FEARNSIDES) ‘‘ Notes on the Lower Paleozoic Rocks of the Cautley District (Sedbergh)’’: Rep. Brit. Assoc., 1910, vol. Ixxx, p- 603.
» 1913. ‘‘ The Lower Paleozoic Rocks of the Cautley District (Yorkshire) ”’ : Quart. Journ. Geol. Soc., vol. xix, pp. 1-18.
‘* The Meres of Breckland’’: Proc. Camb. Phil. Soc., vol. xvii, pt. i (1913), pp. 58-61.
‘© A Tate Paleolithic Site on Wretham Heath, near Thetford ’’: Proc. Prehist. Soc. East Anglia, vol. i, pp. 374-7, pl. xevi.
1914. ‘‘ On the Preparation of a List of Characteristic Fossils’’: Rep. Brit. Assoc., 1913, p. 150, Interim Report of Committee.
1915. (WithG. A. J. CoLE, B. Hopson, J. HORNE, G. A. LEBOUR, A. STRAHAN, W. W. Watts, and F. A. BATHER, Sec.) Interim Report of Committee appointed to consider the Preparation of a List of Stratigraphical Names used in the British Isles in connection with the Lexicon of Stratigraphical Names in course of preparation by the International Geological Congress: Rep. Brit. Assoc., 1914, pp. 113-14.
(With W. G. FEARNSIDES, W. S. BouLTon, E. 8. CosBoLp, V. C. ILLING, and C. LAPworTH) ‘* The Lower Paleozoic Rocks of England and Wales. Report of the Committee appointed to excavate critical sections therein’’: Rep. Brit. Assoc., 1914, p. 115.
1916. ‘‘ The Ashgillian Succession in the Tract to the West of Coniston Lake’’: Quart. Journ. Geol. Soc., vol. Ixxi, pp. 189-204.
The Geology of the Lake District and the Scenery as influenced by Geological Structure, pp. x, 220, 51 text-illust., and map. Cam- bridge University Press.
II.—Awn INVESTIGATION OF SOME WEALDEN SANDS.
By FLORENCE J. RELF, B.Sc. | (PLATE XIL) HE sands which are the subject of this investigation were taken from various parts of the Wealden area, and from different horizons, though all, except the French ones, are below the Weald Clay and represent the lowest division of the Cretaceous rocks, that is, _the Hastings Beds.
Fossils are rare in these sands, but carbonaceous material, indicating plant-remains, is common. ‘The fossils in the Weald Clay are all (except some in the highest part) freshwater forms, and it is generally allowed that the Ashdown Sands are merely an introductory phase of the Wealden Beds. ‘There is, therefore, no question that the whole of this series was deposited by fresh water. It was hoped, however, that an examination of the minerals in these sands might yield some evidence as to their source, and might even throw some light on the much discussed question as to the conditions under which they were deposited.
The comparisons that have been possible are extremely incomplete, and the results are far less definite than it was hoped they would be, but it is still believed that further and more thorough investigations along the same lines would help to a solution of the wider questions to which reference has been made, and that it may therefore be useful to record the results thus far obtained.
The sands originally investigated were taken from the Ashdown Sands of the Wealden area with a view to comparing, first, the sands of one horizon in different parts of the area, and secondly, a sequence
296 Florence J, Relf—Some Wealden Sands..
of sands in one district. Afterwards, some specimens from a higher horizon of the Hastings Beds in the Weald and some from the Wealden of the Isle of Wight were used. After these had been examined a short expedition was made to the districts around Calais and Boulogne, which form the eastern area of the Wealden deposits, in order to collect specimens for comparison with those found further west. This expedition was only carried out during the week preceding the outbreak of war, and the hope of visiting other French localities has had to be abandoned for the present.
The specimens examined include :—
Ashdown Sand. (1) Seven successive bands from a pit near Forest Row. (2) Ten, in two series, each of five successive bands, from Heathfield. (3) Six in succession, from Battle. (4) One from Bexhill. (5) One from Eridge. (6) Three from Lindfield. Tunbridge Wells Sand. Two specimens from south of Ardingley. Wealden of Brook Bay, Isle of Wight. One specimen. Horizon doubtful—above Purbeck and below Gault. S. Etienne au Mont) Equihen Wissant, south-west of Calais.
south of Boulogne.
These last-named specimens were taken from beds which are generally considered to be representatives of our Wealden strata, though their exact horizon has not been determined.
In the field the sands are generally yellowish in colour, and iron- stained. Where the iron is abundant, highly resistant layers are formed, while, in some places, a regular ironstone—that formerly worked in Sussex—is present. Bands of more clayey material are common, while in some parts the usually fine sand is replaced by a conglomerate with pebbles reaching a diameter of about 42",
Meruop oF INVESTIGATION.
The method adopted in examining these sands was the usual one of separation by heavy fluids. ‘The specimen was crushed in a mortar, a process rendered necessary by the amount of iron present, and then boiled in 20 per cent HCl to remove the irony accretions and so clean the grains. ‘The removal of the iron was not always attained by this method. It was not necessary to sift the sands, for they were generally fairly uniform in grain. After treatment with acid the material was washed in running water to remove the mud; then it was filtered and dried. Next a separation was carried out in a solution of KI Hg I, of a specific gravity varying from 2°873 to 3131 in order to separate the heavier minerals from the quartz, the commonest constituent of the sands.
In two cases a double separation was made, the material which came down in the potassium mercuric iodide being filtered, washed, and dried, and then put in a solution of cadmium borotungstate with
Florence J. Relf—Some Wealden Sands. 297
a s.g¢. of 8°317. This separated the heavier minerals from the tourmaline.
It was found advisable to use a fairly large quantity (10 to 20 grams) of sand to begin with, to ensure a greater degree of accuracy in subsequent calculations. In each case the proportion by weight of the heavy material was worked out and the size of the minerals noted.
As a result of these investigations it was found that the sands are composed chiefly of quartz, but that there is a small proportion of heavy minerals, notably of tourmaline and zircon. Other minerals found include felspar, rutile, anatase, staurolite, kyanite, garnet, and fluor. : ‘
WEIGHT OF HEAVY MATERIAL IN 1 GRAM OF SAND.
; Gram. Forest Row. A ‘ A 4 5 -003 > i 3 3 - -0015
-0023 -Average -0014. - 0003 -0003
Battle.
0015 001 Pee Average -0016. -003 | -0012 Hridge. -0008
Lindfield. -0052
-009 } Average -0071. 0025 \ -002 J -0008 -0004
Ardingley. - Average - 0022.
Hquthen. Wissant.
BSaQureUneOQsHowrrynaw
RESULTS OF DOUBLE SEPARATION.
Forest Row. C. . Of the material with s.g. above 3-131, 22 per cent had s.g. lower than 3-317 (this was mainly tourmaline), and 78 per cent higher than 3-317 (this was mainly zircon).
MINERALS.
Quartz.—The quartz grains vary in size from ‘03 mm. to ‘13 mm., the average being about ‘07 mm. They are usually angular, though occasionally they are sub-rounded. The grains generally contain inclusions which are not, as a rule, arranged in any definite lines.
Felspar.—Orthoclase felspar is present in very small quantity only. As the result of an attempt to separate this mineral from the quartz by specific gravity, after the minerals heavier than quartz had been removed, it was found that the amount of felspar obtained from about 10 grams of the material was barely sufficient to weigh, there being only enough material to mount under one small coverslip. The felspar fragments are, on the whole, much smaller than the quartz, and, as is usual with very small fragments, they are even less rounded.
Zircon.—The zircon crystals in the sands show, as they commonly do, very good crystal shape, and they are seldom broken. The individual crystals vary, however, and four types have been noted :—
298 Florence J. Relf—Some Wealden Sands.
(1) Crystals long, length four or five times breadth, with sharply pointed pyramids developed at both sides. (Pl. XII, Fig. 1.)
(2) Crystals short, length about twice the breadth, with pyramids at both ends.
(3) Crystals with only one pyramid developed. These may show a basal plane at the other end, or they may appear irregular at that part, as though broken off (as they would look if they had grown in a cavity). (Pl. XII, Fig. 2.)
(4) The fourth type is a modification of types (2) and (8), and includes short crystals rounded at the ends, making the whole fragment oval in shape.
Of these, type (2) seems to be commonest. Many crystals have inclusions; a few show zoning.
Some idea of the abundance of zircon crystals can be obtained from the results of counting in the case of eleven specimens from Heathfield. In 1 gm. of sand the zircons varied in number from 55 to 877, the average being 288. Though the figures are certainly not accurate they serve to show that the mineral is common among the heavy constituents. In the heaviest portion of the sand (s.g. above 3°317) it is the predominant mineral. The size of the crystals is fairly constant, the length varying, in the examples measured, between — °04 to °09 mm.
Tourmaline.—Next to zircon, among the heavy minerals of these sands, tourmaline is the most abundant, and the blue and the brown varieties are present. The brown tourmalines are generally larger than the blue ones, and they have quite irregular outlines. The blue ones are as usual more definite in shape, often showing a tendency to | prismatic form. Individuals of both varieties are generally broken, but seldom rounded. (PI. XII, Fig. 3.) Their size is less variable than that of the quartz grains, being from ‘05mm. to‘lmm. As a result of the counting previously referred to, the number of tourmaline grains per gram of sand was found to vary from 12 to 105, the average being 58, far less than the number of zircons.
Rutile comes next in point of abundance. The crystal shape is generally good, and the characteristic geniculate twinning is occasionally recognizable.
Staurolite.—This mineral is rare, but a little was identified in the sand from Lindfield, and more in that obtained from west of Bexhill.
Kyantte also is rare, and was only found in the Bexhill specimens and in those from France. (Pl. XII, Fig. 5.)
Anatase, although not common in these sands, was recognized in ~ the Bexhill and Lindfield samples. Some crystals show the striated steep pyramid-faces, and others are tabular. (Pl. XII, Fig. 4.)
Garnets were only recognized in the Lindfield Sands.
Fluor was identified in one of the Lindfield samples.
As the materials found in these sands make it probable that the rocks from which they were originally derived were of granitic character, it was decided to powder some granite and to attempt a separation of its heavy minerals by the same method as that used for the sands. The granite chosen was from Corndon, Dartmoor, this being the nearest granitic area to the Weald. It was crushed in
Florence J. Relf—Some Wealden Sands. 299
a mortar, and sifted through muslin. This method has been adopted at Bedford College, because it is difficult to ensure that no foreign grains are clinging to an ordinary sieve. The fine material was washed to remove the mud, treated with acid, and finally separated in KI Hele. As a result it was found that nearly all the heavy particles consisted of brown tourmaline, generally irregular in shape, but cceasionally prismatic. Zircon crystals were comparatively rare. Some corundum was found. The rarity of free zircon would, of course, be explained by the fact that it commonly occurs included in quartz and biotite, which in this case was not broken up.
On the whole, the result of this examination confirms the idea that the sands were mainly derived from a granitic rock. It remains to seek a large area occupied by suitable rocks, and exposed to denudation in the early part of the Wealden period.
During Jurassic times there was probably a large land area to the west and south-west of the present position of Great Britain. This land included the western mountainous districts of Wales, the Cornwall and Devon Peninsula, and the north-western peninsula of France; but these portions of modern Europe represent the eastern seaboard only of the supposed continent, which is thought to have extended into Ireland, and far to the south-west and north. It is the area referred to by Professor Bonney,} in an article on ‘‘ Pebbles in the Trias ’’, as ‘‘the ancient mass of Archean crystallines, which once swept round the Scoto-Scandinavian region to north-western France’’. In the Portland epoch the borders of this land extended eastward into Dorsetshire, and in the succeeding Purbeck and Wealden periods, continued upheaval had still further increased the land area.
When the Ashdown Sands were being deposited, the greater part of England must, therefore, have been land covered by Jurassic deposits, that 1s, mainly by dark shales and limestones—not the kind of material from which a quartz sand could be derived. The only parts not covered by Jurassic rocks were the areas which had formed part of the western continent, with, perhaps, a fringe of Triassic rocks; and the extreme east of England, north-east of the London Basin. As far as can be judged by borings in this eastern district (at Harwich and Ware, for example), this land area seems to have been formed, at that time, by rocks of Silurian and Devonian formations, which were composed of beds of shale, with thin beds of limestone in the Silurian and of grey and red sandstone or quartzite in the Devonian.
It seems, therefore, fair to conclude that the source of supply of the sands under consideration must be sought among the rocks of the western continent. In the remains of it which have survived to the present time are masses of granitic rock, and from such rocks there is, as we have seen, no difficulty, mineralogically, in deriving the Wealden Sands.
The general angularity of the fragments makes it probable that the material was brought directly from the granitic rock to its present
1 Professor Bonney, ‘‘ Pebbles in the Trias’’: GOL. MaG., Dec. IV, Vol. II, 1895.
300 Florence J. Relf—Some Wealden Sands.
position, and not from any intermediate sandstone. The only sand- stone which need be considered in this connexion is the Trias of the West and Midlands; but according to Dr. Thomas’ the quartz grains in this formation are more rounded than those of the Wealden Sands, not less so, as must have been the case if the Wealden material had been carried from the Trias areas. Further, it is probable that, at that time, the Trias rocks were covered by Jurassic deposits which have since been denuded. Any river flowing eastward from the western land would naturally flow over these Jurassic rocks, and would carry away some of their material. That so little of it is now found in the sands would be explained by its generally calcareous nature.
Some interesting specimens were found, however, in the Ashdown Sand from the neighbourhood of Lindfield, whose nature seems to indicate a derivation from Jurassic rock. In a sandpit north-east of Lindfield, east of Paxhill (the most westerly area considered in the Wealden district), is a layer in which the size of the fragments reaches i_1", They are, in fact, small pebbles firmly cemented to form a conglomerate. The pebbles in this conglomerate have been examined in microscope slides, as well as in the hand-specimen, and are found to consist mainly of quartz, some being vein quartz. But, in addition to these, are certain small lumps of white earthy-looking material. These are evidently the fragments to which Topley refers as ‘‘white chalky-looking stuff’.? Some of it breaks easily in a powdery fashion, but it is not soluble in HCl, and when the hardness of some of the less powdery pieces was tested it was found impossible to scratch them with a penknife. ‘The white material is evidently not calcium carbonate. In some pieces the powdery character is confined to the outside, the inside appearing chalcedonic. Under the microscope the white crumbly stuff was found. to have a great resemblance to decomposing chert, and a gradation seemed. traceable from this to a normal chert pebble. This discovery led to a comparison with several slides* of Jurassic chert from the Vale of Wardour and the Isle of Portland, and the comparison confirmed this opinion and showed that the Lindfield fragments closely resemble the Isle of Portland chert. Further search with a lens, in the hand- specimens, and with microscope revealed small pebbles with the oolitic structure and decided cherty appearance common in these Jurassic rocks. (Pl. XII, Fig. 6.) The presence of this material therefore strengthens the view that the water bearing the Ashdown Sands came from a westerly direction.
It may be noted here that at Lindfield there are found a greater proportion of heavy minerals, larger fragments, and more variety of material—especially among the heavy minerals—than there are elsewhere in the Weald. This points to the probability that here we are near the middle of the old Wealden Channel.
The west to east extension of the Wealden beds gives additional
1 Dr. H. H. Thomas, ‘‘ Petrography of the New Red Sandstone’’: Q.J.G.S., 1909.
2 W. E. Topley, The Weald (Survey Memoir), p. 84.
* These slides were kindly placed at my disposal by Dr. C. A. Raisin at Bedford College.
Florence J. Relf—Some Wealden Sands. 301
support to the view that the stream bearing their material came from a westerly direction. If it did—and this was Jukes-Browne’s view —it would, of course, be probable that tributaries joined it on its way to the southern sea. A tributary from the north-west coming over the Trias rocks of the Midlands may have brought the pebbles of liver-coloured quartzite mentioned by Lamplugh? as occurring in a boring at Dover, and considered by him to have come from the north-east.
On the whole, this study of the minerals in the Ashdown Sands points to the conclusion that the majority of the material was brought by a large river from the west or south-west. On the question as to whether - the Wealden beds were laid down in a lake’ or as a delta, the results of the investigation have been disappointing. Although the Wealden river is believed finally to have reached the sea which then occupied the Mediterranean area, the only known estuarine deposits of that age which are of any considerable importance are those in ° the Haute Marne district. If the Wealden river and the Southern Sea were connected through this area, the subsequent invasion of the Vectian sea north-westward would have been the natural one of advance up a river valley. iS
If the theory that the Wealden river broadened into a lake be accepted, an outflowing stream must be supposed to have emerged from the south-east end, and this stream to have broadened no a delta which was subject to invasion by the sea. If the lake did exist, the stream emerging from it must have been fairly free from sediment, and the thinning of the Wealden deposits, eastward, bears out this view. In this case it is difficult to imagine how all the material necessary to the formation of deltaic deposits could have been accumulated between the lake and the sea. It is true that the Haute-Marne estuarine series is only about 60 feet thick, but it extends over a fairly wide area, and represents a greater amount of
erosion than seems possible between the lake and the delta, unless a stream from another direction joined in at this point; and of this there is, I believe, no evidence.
On the éther theory—that our Wealden Series is estuarine—the assumption is that the deposits are only part of the wide estuary, of whose lower end there are still remains in France. The alternation of clay and sandy material, and the facts that the Weald Clay is less sandy than the underlying Ashdown Sands and that current bedding frequently occurs, are characteristic of lake as well as of delta deposits, if the lake is fed by streams with fairly swift current ; while the absence of rock-salt and gypsum is no proof that a lake did not exist. ‘The absence of marine bands from all but the upper part of the Wealden Series has been used as an argument against their being estuarine, but if this area was but the upper end of a delta their absence from the lower and presence in the higher horizon is but natural. De Lapparent held the estuarine view, “and he stated that the river in question is only one of several which entered the sea from the north.
' G. W. Lamplugh, Mesozoic Rocks in Coal Explorations in Kent, p. 19.
302 Dr. F. A. Bather—A Cidarid from Hartwell.
Whichever theory is held, there is always the difficulty of the gap between the undoubted estuarine deposits of France and the English freshwater beds on the one side, and the marine deposits of the. south on the other, and unless these gaps can be bridged it is doubtful whether any definite solution of the problem can be found.
I have to thank Dr. H. H. Thomas for his kindness in looking at the slides and reading the manuscript. I have also to offer my thanks for being allowed to carry on this work at Bedford College; and especially to Miss Raisin for much help throughout the
investigation.
EXPLANATION OF PLATE XII. Fic.
1. Heavy grains from Ashdown Sand of Forest Row (separated by heavy fluid, s.g. 83-0317), showing slender zircon crystals, one terminated by a pyramid at each end. x 60, approx.
2. Heavy grains from Hastings Sand of Bexhill (separated by heavy fluid, s.g. 3-292), showing zircon crystal withinclusions. Crystal terminated at one end by pyramid faces and at the other probably by a basal plane. x 90, approx.
3. Grains of Ashdown Sand from Forest Row, sinking in solution of mercuric potassium iodide (s.g. 3-0317), but floating on solution of cadmium borotungstate (s.g. 3-317), showing mainly tourmaline. 30, approx. _
4. Heavy grains from Tunbridge Wells Sand of Lindfield (separated by heavy fluid, s.g. 3-035), showing tabular crystal of anatase. x 85, approx.
5. Heavy grains from Wealden Sand of Equihen (Boulonnais) (separated by heavy fluid, s.g. 3-035), showing kyanite with cleavages. x 80, approx.
6. Section of conglomerate in Tunbridge Wells Sand from Lindfield, containing one small pebble of chert, showing structures which include one spiral organism. x 20, approx.
III.—A Ciparr From tHE Harrwett Ciay. By F. A. BATHER, M.A., D.Sc., F.R.S. (Published by permission of the Trustees of the British Museum.)
EMAINS of Echinoderms are so rare in the Hartwell Clay of Buckinghamshire, and when found so fragmentary, that it may be worth while drawing attention to a small piece of an Hchinoid test recently obtained from the Hartwell Brick-pit by Mr. Edwin Hollis, F.Z.S., curator of the Aylesbury Museum, and presented by him to the national collection (Brit. Mus., Geol. Dept., H12241). The terminology of the following description is that defined on pages 59-65 of my ‘‘ Triassic Echinoderms of Bakony”’, Budapest, 1909.
The fragment represents the greater part of two adjacent inter- ambulacral plates of a Cidarid. The portion missing is the adradial tract. It can be inferred from the faces of the transverse sutures that these plates come from the right-hand (or 4) column of the inter- ambulacrum. In the interradial suture-margin of each plate the apicad limb is about twice the length of the orad limb, whence it may be inferred that the plates come from above the ambitus. But since the height of the lower plate is slightly less than that of the upper, they cannot have been far above the ambitus.
Grou. Maa., 1916. Pruate XII.
SOME WEALDEN SANDS.
Dr. F. A. Bather—A Cidarid from Hartwell. 303
The measurements in millimetres are as follows :— Upper plate. Lower plate. Height . 65 6°05
Apicad- interradial margin . Orad-interradial margin Height of scrobicular circle Width Diameter of boss (ill- defined, say) Width of serobicule ,, a Diameter of platform ; Vertical diameter of mamelon Transverse Hi
From this it will be seen that the perebieular circle is compressed, so as to be somewhat elliptical transversely ; the scrobicules, however, remain distinct. Taking the general thickness of the extra-scrobicular region as 1-4 mm., including the tops of the secondary tubercles, the boss rises, with a slightly convex curve, to a platform at 1 mm. above this. The platform is marked with twelve distinct crenelle. The mamelon, which expands slightly, reaches *8 mm. above this.
The interradial tract is covered with secondary tubercles, of which five lie in a lineal space of 4.4mm. They tend to run in lines approximately parallel to the two limbs of the interradial margin. The boss of a secondary tubercle may have a diameter of as much as ‘7mm. Between the secondary tubercles are scattered much smaller tertiary tubercles, which occasionally form partial scrobicular rings.
The main tubercle can hardly be said to have a ring of scrobicular tubercles, for the tubereles surrounding the scrobicule are certainly not larger or more regular than the other secondary tubercles. Indeed, they seem in some cases to be smaller, as though invaded by the _ main scrobicule. On the intertubercular tract bordering the apicad margin of the upper plate there can be distinguished a line of these tubercles, gradually diminishing in size. On the corresponding tract of the lower plate there is an irregular ridge, but the tubercles from which it has been derived have atrophied.
The species which this specimen most resembles are two found near Boulogne-sur-mer, namely Ctdaris legayi Sauvage & Rigaux (1872) and Cidaris boloniensis [melius bononiensis| Wright (1857), neither of which has yet been recorded from England. Descriptions, -Grawings, and bibliography of these will be found in G. Cotteau, Paléontologie Frangaise, Jurassique, vol. x, part 1, EchinidesRéguliers, pp. 214 (1877) to 226 (1878), pls. 200-202. In C. bononiensis, as compared with the present specimen, the scrobicules are more distinct, the scrobicular ring more complete, and the scrobicular tubercles more developed in comparison with the other secondary tubercles. In C. legayi, Cotteau’s figure shows the scrobicular tubercles as less pronounced than in C. dononiensis, but still as more pronounced than the secondaries; his text, however, states that they are of almost the same size as the latter. Our specimen therefore seems to lie between these two species, but rather on the side of C. legayt.
C. bononiensis comes from the Kimmeridgian, C. degayi from the Portlandian zone of Ostrea expansa, that is to say, the Upper Portlandian. he Hartwell Clay is generally regarded as Lower
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4°3 2°3
Pe wooo tw 2 RG wa | or Or
304 Dr. Du Riche Preller—Crystalline Rocks, N. Prémont.
Portlandian. We are therefore justified in regarding the present specimen as a mutation from C. bononiensis to C. legayz, and we may refrain from giving it an independent name.
A list of fossils from the Hartwell Clay was published on p. 227 of the Geological Survey Memoir on the Jurassic Rocks (1895), but this records no echinoderm other than Pentacrinus, which name refers, no doubt, to columnals of Zsocrinus, since the true Pentacrinus is not known later than the Corallian age. f
There are, however, other echinoderms from the Hartwell Clay, and if they were omitted from the list just quoted it is probably because Wright said that they came from the Kimmeridgian, to which in his time the Hartwell Clay was referred. They are the following.
Hemipedina morrist T. Wright, Sept. 1855, Ann. Mag. Nat. Hist., ser. 2, vol. xvi, p. 197. Holotype, a fragment of test figured by Wright (April, 1858, Palaeont. Soc. Monogr. Ool. Echinoidea, p. 166, pl. xii, figs. 2, 6), in the Geological Dept. of the British Museum, reed. E 8800. The radioles referred to this species by Wright (1858, p. 167) are in the same Department, regd. 56879. Other tests are registered E 8801-8803.
Hemipedina cunningtont T. Wright, Sept. 1855, Ann. Mag. Nat. Hist., ser. 2, vol. xvi, p. 198. Holotype, a fragment of test figured by Wright (April, 1858, Palaeont. Soc. Monogr. Ool. Echinoidea, p. 167, pl. xii, figs. 3 a, 5), in the Geological Dept. of the British
*Museum, regd. 34567.
‘“« Cidlaris spinosa, Agassiz’’: radioles provisionally referred to this species by T. Wright in 1857 (Palaeont. Soc. Monogr., p. 53), of which one was figured in 1858 (op. cit., pl. xii, fig. 6, not 4* as in the legend, where the reference numbers are in great confusion). Examples of these radioles are in the Geological Dept. of the British Museum, regd. 34566 & 57029; others, collected by Mr. Zedekiah Hunt, are in the Aylesbury Museum. The true Cidaris spinosa is an Oxfordian species, so it was never likely that these radioles belonged to it. They agree closely with the radioles of Cidaris legayt, and doubtless belong to the same mutation O. legayi/bonomensis as the interambulacrals now at last discovered by Mr. Hollis.
IV.—Tue Crysrattine Rock-akEas oF THE PrimonTESE ALPS. II. Norraern Prémonr. By C. S. Du RIcHE PRELLER, M.A., Ph.D., M.I.H.E., ¥F.G.S., F.R.S.E. N the preceding paper! I described the crystalline rock-areas of the Maritime and Cottian Alps: I now proceed to briefly review those of Northern Piémont forming part of the Grajan and Pennine Alps, under three heads— I. The Lanzo Valleys and Gran Paradiso Groups. II. The Dora Baltea (Val d’ Aosta) Area. IIL. The Lanzo, Ivrea, and Val Sesia Area.
They are shown in the sketch-map, Fig. 1. The conclusions in reference to the combined areas of the Piémontese Alps will be stated at the end of the present paper.
1 Grou. MaG., May and June, 1916, pp. 198-205, 250-5.
Dr. Du Riche Preller—Orystalline Rocks, N. Piémont. 305
I. Tue Lanzo Vatieys anp Gran Parapiso Groups.
1. Zhe Lanzo Valleys (Figs. 1 and 3).—The Stura di Lanzo emerges from the Alps and enters the Po Plain close to the town of Lanzo (540 m.) about 380 kilometres north-west of Turin, and discharges into the Po a short distance below that city. The point of exit lies immediately west of Lanzo, where the Stura cuts through a lherzolite wall 400 metres in height. This defile, or chiusa, of St. Ignazio, 3 kilometres in length, thus forms the gateway and drainage exit of what is indisputably the largest, most concentrated, and most diversified pietre verdi area in the Alps, covering, as it does, no less than 600 square kilometres or about 240 square miles. Immediately west of the St. Ignazio defile the Stura divides into two branches—the southern or Stura d’Usseglio, and the northern or Stura Val Grande—from which latter branches off, a few kilometres higher up, at Ceres, the western arm or Stura di Balme. The more or less parallel courses of the three torrents from their sources to their confluence near St. Ignazio are from 20 to 30 kilometres in length. The Usseglio Stura rises in Rocciamelone (3,557 m.), the middle or Balme Stura descends from Uja Bessanese (3,622 m.) and Uja Ciamarella (3,670 m.), and the Val Grande Stura has its source in La Levanna (3,555 m.). Of these four mountains, forming a erest-line of barely 15 kilometres south to north along the Franco- Italian frontier, the first three constitute a formidable calc-schist massif, while the treble-peaked Levanna forms part of the Gran Paradiso gneiss massif. The Usseglio and Balme Sturas have eroded ‘their beds chiefly in pietre verdi, while the Val Grande branch lies, in its upper part, exclusively in the gneiss formation, and traverses’ pietre verdi masses only in its lower course. The floors of the three valleys are from 1,000 to 2,000 metres below the crest-lines of the dividing ridges with steep, often almost vertical mountain sides.’
As is seen from the sketch-plan, Fig. 3, the drainage area of the Lanzo valleys forms approximately a rectangle about 30 by 20 kilometres in length and width, enclosed by four ridges whose extreme points are Rocciamelone and Levanna on the west and Monte Arpone, Lanzo, and Cima Angiolino on the east.2, Within these ridges, the Lanzo valleys with their three parallel divides form a trough or syncline of pietre verdi in two unequal parts: the larger, western part, about two-thirds of the whole, which lies in the calc- schist, and the smaller, eastern part; about one-third of the whole, which lies in the mica-schist formation. These two juxtaposed divisions or old centres of eruption of different age are separated by a narrow strip of calc-schist running south to north from Monte
‘
1 The three Stura valleys, as also the Orco Valley (Gran Paradiso), are easily accessible by roads leading to Usseglio, Balme, Forno, and Ceresole at the upper ends, 1,265, 1,458, 1,226, and 1,613 m. altitude respectively. The Usseglio and Balme Valleys are also known as the Viu and Ala Valleys respectively.
2 The short valley of the Tesso, immediately north of Lanzo, lies, strictly speaking, outside the drainage area of the St. Ignazio defile, but the torrent, rising in Cima Angiolino, belongs to the Stura watershed and forms part of the Lanzo valleys.
DECADE VI.—VOL. III.—NO. VII. 20
Fig. 1. Sketch Map of Crystalline Rock Areas, Northern Piémeont.
ad Me beefed ys 719
wD Ea t
PV=pietre verdi: O=diorite; gr= granite; por =porphyrite ; sy =syenite ; s=peridotite and serpentine; gn=gneiss ; MS = mica-schist. Del. Dd
3173
\ Pir Vatletta277t Pt Ruse
iP 100,009.
Fig. 2. Section of Grivola Ridge, Grajan Alps.
PS=Permo-Carboniferous schist; 'MS=mica-schist; D=diorite; CL =crystalline limestone ; CS =calc-schist ; Pr=prasinites.
Dr. Dw Riche Preller—Crystalline Rocks, N. Piémont. 307
Arpone to Ceres and Monte Bellavarda, as shown in Fig. 3. On the north, the western division is bounded by the Gran Paradiso gneiss, and the eastern division by mica-schist and minute gneiss. The Paradiso gneiss, being the fundamental substratum, probably extends south below the oale: schists and pietre verdi to the Dora—Maira gneiss massif; the mica-schist formafion with pietre verdi is the continuation of the Rocciacorba and Avigliana belt south of the Lanzo valleys and extends north-east from Lanzo to Ivrea and Val Sesia. The calc-schists are in evidence chiefly at the lower levels of the valleys where they alternate with pietre verdi; at the higher levels and on the crest-lines they are very subordinate, and, except on the western ridge from Rocciamelone to Ciamarella, and in the dividing strip already mentioned, appear only in the eroded gaps or saddles of the more resistant pietre verdi masses.
From Mattirolo’s beautiful ‘‘ geo-lithological ”’ contour-map of the Lanzo valleys 1 : 100,000 (1904),' the distribution of the crystalline rocks of the entire area works out approximately as follows :—?
sq. km. cece Lias—Trias Cale-schist with crystalline limestone . 48 = 8 (western division) \Pietre verdi : : . 240 = 40 Permo-Carboniferous /Mica-schist and minute gneiss : 5 OO = IG (eastern division) | Pietre verdi ; ‘ é 5 on LO — Pre-Carboniferous. Gran Paradiso gneiss . ; ; - § 96) 3 16 600 100
The pietre verdi of the two divisions thus represent collectively no less than two-thirds of the aggregate area. The lithological distri- bution of those masses, intercalated in, and resting on the crystalline schists, is extremely complex, for, except the transverse dividing line already mentioned, there is in their kaleidoscopic association no demarcation, sequence, or distinction of level. Yet, on closer examination, the broad limits of certain groups can be defined along the four parallel ridges which, flanking and separating the three valleys, run west to east and converge at the Lanzo defile. The principal groups, generally circumscribed by morainic, alluvial, and detritus belts round their bases, are shown in the plan, Fig. 3, and specified in the following table, in which the names and altitudes refer only to the culminating points. In almost every case the groups, varying in area from 5 to 20 square kilometres, comprise a cluster of minor peaks and spurs, and alike by their formidable bulk and their often pinnacled crests attest the great resistance of pietre verdi to denudation, to which the once overlying crystalline sedimentary schists more readily and long since suecumbed.®
1 Boll. R. Com. geol., 1905, p. 191. At the time of the compilation of this map all the crystalline rocks of the Lanzo valleys were still considered of Archean age without distinction between the age of the mica-schist and the cale-schist formation, the new classification dating from 1911.
2 The earlier works dealing with the Lanzo valleys, etc., by Gastaldi, Strtiver, Baretti, and Bucca from 1871 to 1886 were already quoted in the preceding papers.
3 The ‘local designations Uja, Ciama, Punta, Becca, Bric, Truc, Torre, Rocca, etc., all denote point, peak, summit, crest, crag, etc.
308 Dr. Du Riche Preller—Orystalline Rocks, N. Piémont.
DISTRIBUTION OF PIETRE VERDI IN THE LANZO VALLEYS.
Ringe I, from Rocciamelone to Lanzo, on right of Usseglio Valley ; 36 km. Serpentine: Gran Uja (2,686 m.); Civrari (2,302 m.). Peridotite, lherzolite, and serpentine: Arpone (1,600 m.); Roe Neir (1,516 m.). Rives II, from Croce Rossa to Lanzo, between Usseglio and Balme Valleys; 30 km. Amphibolites, prasinites, and euphodites: ‘Yorre d’Ovarda (3,075 m.); M. Ciaron (1,863 m.). Serpentine: Becca Nona (2,765 m.); Morosa (2,135 m.); Calcante (1,644 m.). Rivek III, from Ciamarella to Lanzo, between Balme and Grande Valleys; 30 km. Serpentine: Uja Mondrone (2,964 m.); Rosso (1,774 m.). Amphibolites, prasinites, and euphodites: Doubia (2,464 m.); Plu (2;201 m:): Rinee IV, from Levanna to Lanzo, on left of Val Grande; 36 km. Amphibolites, prasinites, and euphodites: Bellavarda (2,345 m.).
On the whole, serpentines predominate in the first, amphibolites, prasinites, and euphodites in the second ridge, while in the third the two series are about equal, and in the fourth they are only repre- sented by the Bellavarda complex wedged between the gneiss formation on the left and the mica-schists on the right. ‘The two series of the calc-schist horizon share their aggregate area of about 240 square kilometres in fairly equal proportions ; that of the eastern or mica-schist horizon, occupying 120 square kilometres, is about equally divided between the nucleus of peridotite and lherzolite, and the surrounding belt of serpentine with associated euphodite.
The pietre verdi of the Lanzo valleys appear in all their varieties and at all levels from 500 m. altitude at Lanzo, which town 1s built on serpentine, up to 3,500 metres on the highest points of the central and enclosing ridges. At the lower levels, more especially in the central part of the synclinal trough, they alternate conformably with calc-schist. and crystalline limestone intercalations, having shared in the acute folding and contortions of the latter; while at the higher levels they form enormous banks, cliffs, and bastions like separate massifs, such as the serpentine complexes of Gran Uja, Civrari, Becca di Nona, and Uja di Mondrone, and, again, the amphibolic, prasinitic, and euphoditic groups of Torre d’Ovarda, Ciaron, Doubia, and Bellavarda mentioned in the table.
The chloritic prasinite known as ovardite and mentioned in the preceding papers takes its name from the Torre d’Ovarda group in the Balme Valley, which latter is, moreover, famed for its splendid specimens of garnet, epidote, and other crystals. All the pietre verdi of more or less secondary composition and their schists present their usual actinolitic, glaucophanic, zoisitic, chloritic, and talcose varieties, and are often garnetiferous and eclogitic. ‘They all exhibit the usual marked tendency to chloritic decomposition, i.e. to pseudo-serpentine or serpentinous schist, a phenomenon which applies equally to the
Dr. Du Riche Preller—Crystalline Rocks, N. Prémont. 309
peridotites, lherzolites and associated euphodites of the eastern or mica-schist horizon. In neither horizon do the euphodites appear as deep-seated rocks; they are, on the contrary, associated and inter- stratified with the other pietre verdi at all levels, overlying and underlying, and intercalated in them and the crystalline sedimentary schists quite as often as vice versa. As in the areas of the Maritime and Cottian Alps previously described, so also in the Lanzo valleys the pietre verdi constitute two distinct, juxtaposed, and eminently magnesian series of eruptive and submarine origin, contemporaneous respectively with the Mesozoic calc-schist and the Permo-Carboni- ferous mica-schist formations with which they are intimately associated, and jointly with which they have for long periods been subjected to repeated earth- HOVERS, folding, and intense pressure-, heat-, and hydro-metamorphism.! °
2. The Gran Paradiso Massif (Fig. 1).—This oval-shaped complex, about 30 by 20 kilometres in length and width, is bordered on the _ south by the Lanzo valleys and on the north by the Dora Baltea watershed. At its southern extremity it is traversed by the Val Grande Stura already referred to, while its central part is intersected west to east by the Orco, which rises in Punta Galisia (3,345 m.) and with its affluent the Soana discharges into the Po. In the northern part rise the Cogne and Savaranche torrents, both of which drain into the Dora Baltea near Villeneuve, above Aosta. ‘The Orco Valley has cut the original dome-shaped massif into two more or less parallel ridges, the southern from the treble-peaked Levanna to Monte Tovo (2,575 m.), and the northern which, starting from Punta Galisia, culminates in the classic ellipsoid or flat cupola of Gran Paradiso proper (4,061 m.), the highest point of the Grajan Alps.
The massif is composed of three more or less concentric masses, viz., a nucleus of primitive, granitoid, porphyroid, glandular, and eye-gneiss with large felspar crystals up to 10 centimetres, surrounded by an inner belt of smaller-grained, schistose, biotitic gneiss with green nodules, and an outer belt of mica-schist and minute gneiss, often with white mica. Of the biotitic gneiss a large lenticular mass in the primitive gneiss crops out at Ceresole (1,613 m.) in the upper Oreo Valley, between La Levanna and Gran Paradiso. In this, the central part of the massif, the gneiss is bedded horizontally as the practically undisturbed fundamental substratum ; only the outer belt, more especially at the southern extremity, has shared in the folding and dipping of the Lanzo Valley region.? In juxtaposition to the
1 In a valuable memoir, ‘‘Contribuzione allo studio delle roccie a glaucofane, ete., Liguria e Alpi Occid.,’’ Boll. R. Com. geol., 1903, p. 255 et seq., S. Franchi has shown that the crystalline sedimentary rocks of the Piémontese Alps, such as silico-caleareous schists (diaspri), quartzites, cale-schists and limestone, mica-schists, phyllites, and minute gneiss, contain glaucophane, epidote, sismondina, zoisite, chlorite, albite, and other secondary minerals as the result of metamorphism of associated and intercalated eruptive material.
* Novarese found a granite vein in a large erratic gneiss block near the Sea Glacier (2,500 m.) in the south-west corner of the Paradiso massif, which may therefore contain intrusive granite, like the Argentera massif in the Maritime Alps. V. Novarese, ‘* Rilevamento Valli Orco e Soana, Alpi Occid.’’: Boll. R.
Com. geol., 1894, p. 215 et seq. A. Stella, ‘“Rilevamento Valle Gre) Alpi Occid.’’: ibid., p. 343 et seq.
310 Dr. Dw Riche Preller—Crystalline Rocks, N. Piémont.
outer belt, a more or less continuous fringe of calc-schist and pietre verdi extends all round the periphery of the massif, stretching from Monte Bellavarda in the Stura Grande Valley north to the Orco and Cogne Valleys and thence north-east to the Champorcher and Clavalité Valleys, where it forms a separate, considerable area. Throughout this belt, the pietre verdi present all the varieties of those of the Lanzo valleys, including more especially glaucophanic amphibolites and omphacitic eclogite. Along its eastern margin this cale-schist and pietre verdi belt is contiguous to the mica-schist horizon with large intercalations of minute and tabular gneiss conspicuous by its green mica; in the Lanzo valleys this gneiss is quarried near Pessinetto, between Lanzo and Ceres. The eastern spurs of the mica-schist area form part of the Lanzo-Ivrea belt to be described later. II. Tae Dora Batrea ARga.
The Val d’Aosta comprises in its middle course important pietre verdi groups, both on the right and left of the Dora Baltea. On the right the most remarkable areas are those of Punta Grivola, Monte Emilius, and Monte Rafré, and on the left the Mont Mary group.!
1. The Grivola Area (Figs. 1 and 2).—About 10 kilometres north of Gran Paradiso, but outside the gneiss massif, and in the surrounding calc-schist formation, rises the Grivola peak (3,969 m.), which in its pyramidal grandeur vies with Matterhorn and Monte Viso. Its position is rendered the more commanding by the scooped out valleys of the Cogne on its eastern and northern, and of the Sayaranche on its western flank, both of which torrents, as already mentioned, rise in the Paradiso massif and discharge into the Dora Baltea near Villeneuve (670m.). The ridge which rises from Villeneuve? between the two valleys to the crest of Grivola and Grivoletta (3,526 m.) in a horizontal distance of 12 kilometres presents, in an interesting natural section, a complete sequence of rock formations which, in ascending order, may be summarized as follows :—
Superficial width. Altitude. Villeneuve. Lias and Trias: Fossiliferous limestone, ordinary ) km. m. facies. ; : j Bille 700 Cale-schist and crystalline lime- stone . Y ; : é 2,000 Becca Piana. Permo-Carboniferous: Sericitic, graphitic, gneissi- form, and psammitic schist Z ‘ : . 1 2,800 Gran Nomenon. Sphenicdiorite . f : : : . 4 3,500 Sericitic, graphitic, gneissiform, and psammitic schist ; : : - é : . 1 3,500 Grivola. Lias and Trias: Crystalline limestone, cale-schist, and prasinites 5 : ‘ : RO BEAN 12 3,200
1 The whole region between the Aosta and Orco Valleys, including the Paradiso massif, is, perhaps more than any other part of the Piémontese Alps, rendered conveniently accessible by the numerous mule paths of the Royal shooting preserves. An excellent topographical map of the Val d’Aosta, Lanzo, and Ivrea region, 1 : 250,000, is that by V. Novarese in Boll. R. Com. geol., 1913-14, p. 244, ‘‘ Il Quarternario Valle d’ Aosta e Valli Canavesi.’’
2 Villeneuve is one of the localities where S. Franchi found fossils in Triassic limestone intercalated in cale-schists. ‘‘Terreni secondarie facies Piémontese’’: Boll. R. Com. geol., 1909, p. 526 et seq.
Dr. Du Riche Preller—Crystalline Rocks, N. Piémont. 311
The upper part of this section is shown in Fig. 4.!_ Its characteristic feature is the Permo-Carboniferous zone which crosses the ridge about midway between and at right angles to the calc-schist formation. The zone or belt is composed of an enormous mass of sphenic diorite which constitutes the Valletta, Ruié, and Gran Nomenon peaks and the intervening Mésoncles and Belleface cols or saddles, and is flanked on either side by considerable banks of sericitic, gneissiform schist and psammitic, carbonaceous sandstone of the greywacke type. The diorite zone, about 4 kilometres in superficial width, extends east into the Cogne Valley and west across the Savaranche Valley to Mont Bioulé on the divide between the latter valley and Val Rhémes. Inthe Cogne Valley it was first recognized by Baretti* in 1876 and described as sphenic syenite, similar to the syenite of Biella; but Novarese showed it to be essentially dioritic, with 63 per cent of Si O,.°
The Savaranche and Cogne dark-green diorite varies in structure from compact to granitoid, gneissoid, and schistose, and is normally composed of plagioclase, hornblende, quartz, black mica, aggregations of minute muscovite, and abundant titanite (sphene) crystals up to 1 centimetre in length. Near Colle Mésoncles it exhibits secondary elements, e.g. albite, epidote, actinolite, with unaltered titanite, while on the Val Rhémes ridge it is essentially fine-grained and massive. ‘lhe mass thus presents an interesting example “of this rock both in its primitive and in its metamorphosed, re-composed, granitoid, and gneissoid form. In upward succession the diorite and gneissiform schist zone is followed by a bank of crystalline limestone, and thence to the summit of Grivola and beyond to Punta Galisia * ‘by a constant conformable alternation of calc-schist and pietre verdi banks, the latter up to 500 metres in depth, as part of the belt which encircles the Paradiso gneiss massif. Here again the pietre verdi, predominantly prasinites with strips of serpentinous schist, appear in
-all their varieties, more especially in the upper Savaranche Valley near Degioz (1,541 m.) immediately west of and below the Grivola
1 This section is founded on the complete one given by Novarese in ‘‘ Profilo della Grivola’’, ibid., p. 497 et seq.
2M. Baretti, ‘‘ Studi Gruppo Gran Paradiso’’: Mem. Acc. Linceo Torino, 1876, p. 195 et seq.
* V. Novarese, ‘‘ Diorite granitoide e gneissiche Val Savaranche’’: Boll. R. Com. geol., 1894, p. 275 et seq.
* The cale- mee of Grivola and Galisia were assigned to the Mesozoic (Lias—Trias) as the equivalents and continuation of the schistes lustrés by M. Bertrand in his ‘‘Etudes dans les Alpes francaises’’, Bull. Soc. géol. France, vol. xxii, p. 69 et seq., 1894, which marked his return from his temporarily Archean to his earlier Mesozoic views on that formation. The latter were confirmed by P. Termier in ‘‘ Les schistes lustrés de la Grivola ’’, Bull. Service Carte géol. France, vol. vii, p- 150 et seq., 1895. The Piémontese cale-schists are, on the whole, more micaceous than the French schistes lustrés, which are more aluminous than the former and to which the designa- tion ‘‘ série cristallo-phyllienne’’ is therefore more appropriate. The super- position of cale-schists on Triassic limestone as verified by Franchi and Termier in various localities also occurs in the Roches d’Ambin massif (Petit M. Cenis, upper Susa Valley), where the minute gneiss and mica-schist are overlain by limestone upon which rests cale-schist.
312 Dr. Dw Riche Preller—Crystalline Rocks, N. Prémont.
peak, where the pietre verdi rocks contain fine specimens of gastaldite (blue glaucophane) and garnet crystals. The Permo-Carboniferous diorite and gneissiform schist zone of the Savaranche and Cogne Valleys is obviously connected with the similar diorite of Locana in the Orco Valley and of the Ivrea and Val Sesia belt to be dealt with later.
2. Monte Emilius (Fig. 1).—A striking contrast to the normal sequence of the crystalline sedimentary and pietre rocks of the Grivola group is presented by Monte Emilius (3,559 m.) and the neighbouring Becca di Nona (3,182 m.), which lie about 12 kilometres south-east ot Grivola, and are separated from the latter by the Cogne Valley. Both mountains, with their extremely rugged and craggy flanks, rise straight from the Dora Baltea Valley between Aosta (580 m.) and St. Marcel to a height of 3,000 and 2,600 metres respectively in a horizontal distance of barely six kilometres. The upper parts and summits of both are composed of minute gneiss and eclogitic, garnetiferous mica-schist, while the lower flanks facing the Aosta Valley consist of huge masses of coarse-grained, gneissiform euphodite more or less parallel to the overlying gneiss and mica- schist. On the Monte Emilius flank the encircling cale-schist formation is not in direct evidence, but on Becca di Nona it crops out above Charvenod close to Aosta and again higher up at the Sismonda signal (2,347 m.), where it rests on minute gneiss. In both places the cale-schist dips at a steep angle in opposite directions, while the gneiss and mica-schist of the upper flanks and summits of both mountains are greatly contorted; near St. Marcel, at the lower end of the valley of that name, they descend to the 700 metres contour and then apparently dip below the calc-schist.
The phenomenon of reversed sequence in the Monte Emilius group is the result of an inverted fold in connexion with the great fracture fault which runs along the Aosta Valley to Chatillon and St. Vincent. From here, instead of following the sharp southward bend of the Dora Baltea towards Ivrea, it extends east across the Brusson Valley to Arcezas, where the calc-schist mass at the base of a great gneiss bank affords striking proof of a similar dislocation near the Conte . with the mica-schist formation of the Ivrea belt.
8. Monte Rafré (Fig. 1).—About 12 kilometres east of Monte Emilius, in the calc-schist and pietre verdi area of the Clavalité and Champorcher Valleys previously mentioned, occurs the remarkable sequence of the Monte Rafré (3,146 m.) and Monte Glacier (3,186 m.) group which forms the divide between those two valleys. In this case, a mass of brecciated prasinitic gneiss which crops out on the crest of the divide, overlies a mass of euphodite metamorphosed to prasinites, in apEanenuy reversed sequence. In reality the prasinites, as Stella has shown,! are an isolated lenticular wedge intercalated in the brecciated gneiss which lies in the calc-schist formation. ‘The latter, with pietre verdi, extends from the Champorcher Valley to
1 A. Stella, ‘‘Gneiss Monte Emilius e M. Rafré’’: Boll. Soc. geol. ital., 1906, p. xlvi. E. Mattirolo, ‘‘ Rilevamento Val Champorcher, Alpi Graje’’: Boll. R. Com. geol., 1899, p. 3 et seq.
Dr. Du Riche Preller—Crystalline Rocks, N. Prémont. 318
Chatillon and Verrés in the Dora Baltea Valley and thence up the Tournanche and Brusson Valleys, whence it skirts the base of Matterhorn and Monte Rosa.
4, Mont Mary.—On the left of the Dora Baltea north of Aosta, and exactly opposite Monte Emilius, rises the Mont Mary (2,875 m.) group, which is the counterpart of the former and exhibits a similar reversed sequence. ‘he calc-schist appears here at the base, and is overlain by Permian schist, upon which rests the cupola of garneti- ferous mica-schist. The group, which includes Gran Becca (2,967 m.) and Gran Col (2,864 m.), lies in the zone of the same fracture fault and presents the same phenomenon of an inverted fold as Monte Emilius on the opposite side of the valley. From the Mont Mary group the mica-schist formation extends up Val Pellina and across the crest of the Pennine Alps to Dent Blanche (4,364 m.), north-west of Matterhorn.!
The great intrinsic geological interest of the crystalline rock-areas of the Aosta valleys described in the foregoing has in recent years been enhanced by Lugeon and Argand having included them in their grand series of overthrust sheets in that and other parts south of the crest of the Alps.? According to their theory, worked out from ingenious geometrical designs, the Gran Paradiso, Grivola, Grand Nomenon, Emilius, Rafré, and Mary groups are not ‘‘ rooted” or ‘‘autochthonous’’ massifs, but cover-sheets (nappes de recouvrement) pushed over from different directions and more or less considerable distances. Investigations instituted by the Italian Geological Survey in 1905,5 and notably by Novarese in 1909,* have, however, conclusively shown that the cupolas of those groups differ strati- graphically and lithologically from the ‘‘ root”? areas whence they are supposed to have been derived, and that, with the exception of the small, isolated massif of Monte Pilonet (2,697 m.) between the Tournanche and Brusson Valleys on the left of the Dora Baltea, ‘where the gneiss cupola completely covers the cale-schist, there is no evidence at all of extensive overthrusts in that part of the Alps.
1 VY. Novarese, ‘‘ Gneiss Monte Emilius e M. Mary’’: Boll. Soc. geol. ital., 1912, p. 31. Novarese describes an interesting section of granite, mica-schist, and diorite i in a railway cutting ne wmeea Aosta and Quart, on the left of Dora, below M. Mary.
2M. Lugeon & E. Argand, ‘‘ Grandes Nappes de Recouvrement de la zone du Piémont. Homologies ditto’’ : Comptes rendus Acad. Sciences, Paris, Mai 15 et 29, 1905.
3 “*Relazione’’: Boll. R. Com. geol., 1906, p. 27.
4 V. Novarese, ‘‘ Profilo Grivola’’: Boll. R. Com. geol., 1909, p. 497 et seq. A. Stella, op. cit., 1912, p. xlvi. ‘‘ Problema geo-tettonico Ossolae Sempione”’ : Boll. R. Com. geol., 1905, p. 5 et seq. S. Franchi, “‘ Tettonica della Zona del Piemonte ’’: ibid., 1906, p..123 et seq.
(To be concluded in our next Number.)
314 Dr. C. A. Cotton—Later Geological
V.—Tar Srructure anv Later GerontocicaL History oF New ZEALAND.
By C. A. Corton, D.Sc., F.G.S., Victoria University College, Wellington, N.Z. (Concluded from the June Number, p. 249.)
UPPORTED by the great weight of Hutton’s authority, his views, with which those of Haast 1 and the early views of Hector” were in general agreement, have gained wide acceptance, notwithstanding the opposition of McKay. Marshall, for example, as late as 1911 wrote as follows: ‘‘ The great elevation [ Mesozoic orogenic movement] was succeeded by nearly as great a depression. The majestic mountain ranges were gradually lowered until nothing but a chain of islands showed above sea level. ‘lo what a great extent this movement prevailed is seen at Lake Te Anau, where the Oamaru formation, some 8,000 feet thick, rises to the tops of the mountains. At Wakatipu and in the Rangitata valley the Oamaru rocks are found in the recesses of the mountains. In the Trelissick basin and between the masses of the Kaikoura ranges there was deep water. The valleys of the tributaries of the Buller are filled with Oamaru sediments.” §
Brief reference may here be made to the effects of the Kaikoura movements, though anything like a complete account of the structure and surface forms produced cannot be attempted. In Marlborough the great reverse faults, first noted by McKay, and the huge tilted and compressed blocks from which the Kaikoura ranges have been carved are most impressive.* Though less intense the effects in North Canterbury are similar in kind, and a geological map of the district would present the appearance of a mosaic of ‘ oldermass’ and ‘covering strata’ formations as a result of block faulting, with the preservation of the latter on the lower blocks and their removal by erosion from the higher.
Some remarkable intermontane basins occur as a result of these movements,° and the rivers that cross the basins flow out of them by way of deep, perhaps antecedent gorges across the oldermass of the upthrown blocks. ‘The largest of these structural basins, the Waiau— Hurunui Plain, may be mentioned as an example. It is traversed by two rivers of considerable size, the Hurunui and the Waiau, which, curiously enough, make their way out by separate gorges, while the lowest initial gap in the basin rim—as indicated by the structure of the covering strata—is not occupied by a stream at all. A railway enters the basin from the south by way of this gap. The covering strata are in part preserved in the low-lying interior of the
1 J. von Haast, ‘‘On the Geology of the Waipara District’’: Col. Mus. and Geol. Surv. of N.Z., Rep. Geol. Expl. 1870-1, pp. 5-19, 1871.
2 J. Hector, ‘‘On the Geology of the Manuherikia Valley’’: Otago Prov. Goy. Gaz., 1862.
3 P. Marshall, ‘‘New Zealand and Adjacent Islands’’: Handbuch reg. Geol., Bd. vii, Abt. i, p. 40, Heidelberg, 1911.
4 See C. A. Cotton, ‘‘ Physiography of the Middle Clarence Valley ’’: Geo- graphical Journal, vol. xlii, pp. 225-46, 1913.
5 R. Speight, ‘‘ The Intermontane Basins of Canterbury’’: Trans. N.Z. Inst., vol. xlvii, pp. 336-53, 1915.
History of New Zealand. 315
basin and are largely covered by young fluviatile gravel. Numerous other similar but smaller structural basins occur, the covering strata within which are more or less eroded or buried under fluviatile gravel according to their position with respect to local base-levels. It is evident that here, as in Marlborough, faulting has been accompanied, if not actually brought about, by a compressive force, for the covering strata are thrown into folds.
From some of the uplifted blocks the surfaces of which were merely tilted slightly from their former horizontal attitude little below the base of the cover has been removed by erosion, and remnants are thus preserved of the fossil denudation plain which, in places at least, forms the floor of the cover. As an example the western slope of Mt. Grey may be cited. Farther to the south-west the outer ranges of the Southern Alps are composed of irregularly uplifted blocks, upon the tops of which are preserved remnants of a surface of small relief possibly also stripped of a cover.
In the Oamaru district the base of the covering strata is of early Tertiary age, and the beds le upon a plane-denuded surface of the oldermass. There is less evidence of compressive stress here accompanying the Kaikoura movements, but the beds are thrown into broad folds. The open-water character of the sediments of the cover and the absence of coarse clastics are sufficient to show that the mountains to the west, into the valleys of which the covering strata now penetrate, were not in existence as a high land-mass during the period of deposition. ‘The structure and physiography suggest that the cover had formerly a great westward extension, and this is proved by their occurrence as narrow strips in trough depressions,
-e.g. in the Shag and Waitaki Valleys. An account of the structure
of an in-faulted outlier of the cover at Wharekuri, Waitaki Valley, has recently been given by Marshall.' Inland occurrences of the Tertiary rocks are thus easily explicable, and the theory of their . deposition in fiord-like arms of the sea, which was advocated for so long by Hutton, must now be regarded as definitely abandoned.
In the Oamaru district large, gently sloping, flat areas of the fossil denudation plain forming the floor of the covering strata have been stripped but not destroyed. Some are seen to dip beneath the outcrops of the cover, as, for instance, south-west of Oamaru, and also in the Waihao basin north of Oamaru, where the presence of such a surface has been noted by Thomson? (see Fig. 2). Others occur on the tops of high mountain blocks differentially uplifted and tilted in various directions. Other and larger portions of the high blocks have been maturely dissected, and dissected fault-scarps are of common occurrence.
Farther to the west, in Central Otago, the landscape is a mosaic of blocks the general nature of which has been recognized by McKay?
1 P. Marshall, ‘‘ Cainozoic Fossils from Oamaru’’: Trans. N.Z. Inst., vol. xlvii, pp. 380-1, 1915.
2 J. A. Thomson, ‘‘ Coal Prospects of the Waimate District, South Canter- bury’’: Highth Ann. Rep. Geol. Surv., 1914, p. 160. -
3 “* On the Origin of the Old Lake-basins of Central Otago ’’: Col. Mus. and Geol. Surv. N.Z., Rep. Geol. Expl. 1883-4, pp. 76-81, 1884 (p. 80).
Dr. C. A. Cotton—Later Geological
316
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History of New Zealand. 317
and by Park.! A group of the lower-lying blocks determines a chain of basins, which have been known in the past as ‘‘ old lake-basins ”’, though no definite evidence has been adduced that they have been occupied by lakes. The depressions now occupied by large lakes still farther west—e.g. Wakatipu and ‘le Anau—were probably, as Andrews” notes, initially of thesame nature; but they have been subsequently profoundly modified by glacial erosion. In Central Otago the covering strata are largely of terrestrial origin and have been preserved over considerable areas on the low-lying blocks in the basins. If, as is probable, there was formerly a continuous or nearly continuous cover on the higher blocks also, it has been removed by erosion, with the exception of a few outliers. The general nature of the Kaikoura deformation is here decipherable, not only from the attitude of the cover in the basins, but also from the configuration of the higher blocks upon which extensive areas of a denudation plain, warped and dislocated by the movements, are preserved. As the plain dips beneath the cover on the flanks of tilted blocks and as it supports outliers of the same beds, it is, at least in great part, a stripped floor. Its virtual continuity with the stripped floor in the Oamaru district indicates with a high degree of probability that it is a part of the same erosion surface, though perhaps not covered until a later date and perhaps never submerged. ‘The majority of the blocks in Central Otago are elongated, trending north-east and south- west, and are tilted towards the north-west, presenting scarp-faces towards the south-east or east.* Kast of the centre of the district a considerable area of the denudation plain forms a more or less horizontal plateau at a height of about 1,000 feet. This has been _ealled the ‘‘ Central Otago Peneplain ” or Barewood Plateau.*
In the North Island the absence of a continuation of the main mountain range—the Southern Alps—of the South Island has often been remarked upon, and the statements of Hutton °® and Suess * on the . Subject are perhaps correctly interpreted as indicating their belief that the north-eastern continuation of the Alpine range has subsided independently. In view, however, of the late date of the movements to which the South Island ranges owe their present height, and in view also of the presence in the North Island opposite those ranges of Tertiary rocks of greater age than the orogenic movements, it would be more correct to say that this portion of the North Island has merely not been uplifted to the same extent as the South Island.
1 ““The Geology of the Area’ covered by the Alexandra Sheet, Central Otago Division,’’ N.Z. Geol. Sury., Bull. 2, p. 6, 1906; ‘‘ The Geology of the Cromwell Subdivision, Western Otago,’’ N.Z. Geol. Surv., Bull. 5, 1908.
2 E. C. Andrews, ‘‘ Erosion and its Significance’’: Journ. and Proc. Roy. Soc. N.S.W., vol. xlv, p. 116, 1911.
3 The structure of this district is well displayed by an excellent geological map by A. McKay in his Report on the older Auriferous Drifts of Central Otago, 2nd ed., Wellington, Govt. Printer, 1897 (opp. p. 84).
4 J. Park, loc. cit., 1906 and 1908; Geology of New Zealand, 1910, p. 9.
> F. W. Hutton, ‘* Sketch of the Geology of New Zealand ’’?: Quart. Journ.
Geol. Soc., vol. xli, p. 197, 1885.
' © #H. Suess, The Face of the Harth (Eng. trans.), vol. ii, p. 147, Oxford, 1906.
318 Dr. C. A. Cotton—Later Geological
The district around Wellington and that characterized by a con- tinuation of the outcrop of ‘oldermass’ rocks to the north-eastward —the axis of the island—has not, however, escaped uplift; and a very general sudden steepening of the dip of the younger strata as the oldermass is approached shows that this uplifted block or series of blocks is bounded by monoclinal flexures or faults.’
Along the eastern base of the Rimutaka Range there is a well- preserved fault-scarp. Here the structure closely resembles that produced by the Kaikoura movements in the South Island. To the east lies a gently tilted block with its cover much folded; and a broad fault-angle depression—the Wairarapa Valley—exists between the black slope of this block and the steep eastern fault-scarp slope of the Rimutaka Range. The broad tectonic depression extends far to the north-east.”
East of the mountain axis the effects of compression are strongly marked, the covering strata being much folded, while westward from the axis they are only very gently tilted. The trend of the features produced by these movements is about north-east, as it is in the neighbouring part of the South Island.
In the northern part of the North Island isolated areas of the oldermass project through the Tertiary formations. To these Suess * refers as ‘isolated fragments of the sunken range”’, and Marshall * expresses agreement with Suess’s statement that the ‘‘ north-west coast in no way represents the actual trend of the mountains ”’.
To the writer the presence of these horst-like masses appears to indicate that the northern portion, in common with the rest of New Zealand, was affected by the Kaikoura movements. From these uplifted areas the covering strata have been removed, and the oldermass has been maturely dissected. In the neighbourhood of the horsts and generally throughout Northern Auckland the Tertiary strata are considerably folded.
Post-Karxkoura MovEmMeENTs.
It is well known that in comparatively recent times some parts of the New Zealand region have been affected by uplift and others by subsidence, while in some parts there is evidence of oscillation. Very brief reference to these movements is all that is possible here. It is important to note, however, that these latest movements generally have the effect, as far as any particular district is concerned, of ‘regional’ as distinguished from differential movements—of epeirogenic as distinguished from orogenic. In a broad sense, however, these movements really are differential, for the New Zealand region has not moved as a whole. Units of much larger size than the blocks associated with the Kaikoura movements have moved independently.
1 J. A. Thomson, ‘‘ Mineral Prospects of the Maharahara District, Hawk’s Bay’’: 8th Ann. Rep. Geol. Sury., Mines Statement, 1915, p. 164.
* Thomson, loc. cit., p. 165.
3 The Face of the Earth (Eng. trans.), vol. ii, p. 44, Oxford, 1906.
4 New Zealand and Adjacent Islands, 1911, p. 25.
History of New Zealand. 319
Tilting of some of the large blocks on a hinge-line may account in some cases for transitions from the features characteristic of uplifted to those of depressed districts, e.g., the northern part of the North Island has been most recently depressed while the southern part has been continuously uplifted, and again in the Marlborough—Nelson district there is a transition from the deeply drowned topography of the Marlborough Sounds through an east-west hinge-line in the vicinity of the town of Nelson to an area farther southward where the last movement has been one of uplift. The depressed Marlborough Sounds district is, however, separated from a very recently uplifted area to the south-east * only by the alluvium-filled Wairau Valley, suggesting the presence here of a fault. Faults of late date appear also to have determined the outlines of at least some parts of the New Zealand coast, especially in and about Cook Strait.”
From considerations of the latter kind alone one might be tempted to conclude that the latest or post-Kaikoura movements are merely a continuation of the Kaikoura movements; and the formation of the harbour of Port Nicholson, Wellington, by the drowning of a system of valleys resulting from a purely local movement of subsidence * appears at first sight to point in the same direction. The Port Nicholson depression is, however, a quite exceptional feature.
If, on the other hand, an appeal for information is made to the physical features of the districts strongly affected by the Kaikoura movements in those parts of Marlborough, Nelson, and Otago that have been uplifted in later times, there is evidence of a long period of rest—during which a cycle of erosion reached an advanced stage— intervening between the two sets of movements. There has, moreover,
_ been no general renewal in later times of movement on the faults of
Kaikoura age‘; and the origins of the earthquakes felt in New Zealand are, with a few exceptions, situated not within the land area but some distance seaward.’ It would seem that, though the _ Kaikoura movements may possibly be not quite extinct, they have very generally been succeeded, after a period of rest, by movements of the mysterious purely vertical kind which appear to have no connexion with compression.
ConcLusION.
Tn conclusion the general nature of the relief of the land may be stated in the following brief diagnosis, in which is emphasized the importance of the Kaikoura movements in comparison with the Mesozoic in determining modern features. New Zealand may be described as a concourse of earth-blocks of varying size and shape,
1 C. A. Cotton, ‘‘ Preliminary Note on the Uplifted Hast Coast of Marl- borough’’: Trans. N.Z. Inst., vol. xlvi, pp. 286-94, 1913.
26. A. Cotton, ‘‘ Fault Coasts in New Zealand’’: Geographical Review, vol. i, pp. 20-47, 1916.
2 C. A. Cotton, ‘‘ Notes on Wellington Physiography’’: Trans. N.Z. Inst., vol. xliv, pp. 245-65, 1912.
4G. A. Cotton, ‘‘Physiography of the Middle Clarence Valley’’: Geo- graphical Journal, vol. xlii, pp. 236-7, 1913.
5 See G. Hogben, ‘‘ Notes on some Recent Earthquakes in New Zealand’”’: Trans. N.Z. Inst., vol. xlvi, pp. 301-3, 1914.
~
320 Professor J. W. Gregory—
in places compressed; the highest blocks lying in the north-east and south-west axis of the land masses, so that the whole structure may be termed a geanticline ; the blocks initially consisting of an older mass of generally complex structure much denuded and largely planed, and concealed, over the greater part of the area, by covering strata which had not been disturbed before the ‘ blocking’ took place; the whole, since these movements, has been considerably modified by erosion somewhat complicated by the effects of later movements of uplift and subsidence.
VI.—Tue Acer or tHE Norseman LimeEsrone, WESTERN AUS!RALIA. By Professor J. W. GREGORY, D.Sc., F.R.S.
| is generally agreed that the main plateau of Western Australia has probably stood above sea-level since the earliest geological times, and has perhaps been a land area since the Archean. Marine deposits lie against its northern, western, and southern borders, but none are known upon the plateau itself; but through the depression of Lake Cowan Kainozoic marine deposits have extended northward into the Dundas Goldfield at Norseman. These marine deposits include a deep lead with sponges which were described by Dr. Hinde (Bull. Geol. Surv. W.A., No. 36, 1910, pp. 7-24, pls. i-ii1) and some patches of limestone which occur on the surface around Norseman. They have been described by Mr. A. Gibb Maitland, 1908 (‘‘ Recent Advances in the Knowledge of the Geology of West Australia,’ Rep. Aust. Assoc. Adv. Sci., vol. xi, p. 153, 1906), and by Mr. W. D. Campbell (‘‘The Geology and Mineral Resources of the Norseman District, Dundas Goldfield,” Geol. Surv. West Aust., Bull. 21, p. 22, 1906).
These Norseman limestones prove that at the date of their deposition the southern margin of the great plateau of Western Australia stood 1,000 feet below its present level (cf. J. W. Gregory, ‘The Lake System of Westralia,” Geogr. Journ., vol. xlili, pp. 656-64, map, 1914). The date of this submergence is of primary importance in the history of the physiography of southern Western Australia.
The suggestion has been made that the limestone is Pleistocene, and I owe to the kindness of Mr. E. 8. Simpson some fossiliferous fragments of the Norseman Limestone which I have examined to see what light they throw on the age of the rocks. The fossils are, however, all in poor preservation. The best preserved of the molluses have been kindly examined by Mr. A. E. Kitson, who, in spite of his extensive experience with the Victorian Kainozoic, is unable to give any very positive determination. He remarks as follows :—
‘‘T have been over the fossils from the Norseman limestone, but am sorry to say I cannot recognise any of them specifically. ‘They all are too fragmentary even for generic determination. Several appear to be fragments of Cardita; others of brachiopods. Two small ones look like young gasteropods (WVatica?), but they may be adult forms of an identifiable species that I do not know. Two appear to be Turritellas. Speaking from memory of TZurritella
Age of Norseman Limestone, Western Australia. 321
pagodula, Tate, the ornamentation in these seems to resemble that of Tate’s species, which is recorded from Beaumaris, Horsham, and the Gippsland Lakes (‘Tate and Dennant’s Upper Oligocene and Miocene). A lamellibranch seems to have the ornamentation of Dosinia (D. Johnstoni ? Tate), which ranges from Tate and Dennant’s Middle Oligocene to Miocene. I do not like the suggested Pleistocene age for these shells. They may be Pliocene equivalent to the Glenelg R. and Moorabool Viaduct beds of Victoria.”
_ The specimens include several Bryozoa of which the preservation is imperfect, but by the aid of enlarged photographs of some of the specimens a fairly probable identification of five species is possible.
Fic. 1. Yocecia of three Bryozoa from the Norseman Limestone. X 6 diam. ,, la. Cellaria rigida, McG. », 10. Macropora clarkei (Ten.-Wds.). », le. Schizoporella convexa, McG. The specimens, however, are so corroded that it is only by piecing together the evidence of several of the zoccia that sufficient material for identification is obtained. The species that are thus provisionally determinable are as follows :— Membranipora delicatula (Busk); Miocene, Victoria; Pliocene and
- Recent.
Cellaria rigida, McG.; Miocene and Recent.
Schizoporella convera, McG.; Miocene, Victoria.
Macropora clarket (Ten.-Wds.); Miocene, Victoria.
Schismopora modesta, McG.; Miocene, Victoria.
M. delicatula was founded on Pliocene material, and both it and Cellaria rigida still live on the coasts of Australia. The three other Bryozoa, of which the identification is more satisfactory, are typical Victorian Miocene species. Schizoporella convexa was founded by McGillivray on material from Muddy Creek, Victoria. All the five species occur in the Victorian Miocenes, and though no positive opinion can be expressed on s0 short a list of fossils, their evidence is in favour of the Miocene rather than of the Pleistocene age of the Norseman Limestone. The material agree more closely with the Miocene of Victoria than with the Pleistocene. The specimens, however, encourage the hope that more extensive collecting at Norseman would yield sufficient fossils to settle the age of this very significant limestone.
DECADE VI.—VOL. III.—NO. VII. 21
322 EH. T. Newton—Trogonthervwm from Copford, Essex.
VII.—ZroGonTHERIUM FROM THE PLEISTOCENE OF CoprorD, Essex.
By EH. T. NEwtTon, F.R.S., F.G.S., F.Z.S.
N the year 1852 John Brown, of Stanway, published a paper on the Copford deposits (Q.J.G.8., vol. viii, p. 184), and in this includes a letter from George R. Waterhouse referring to two ‘Beaver’ teeth and the metacarpal of a Bear. One of these teeth is described and figured, and is said to differ from the beaver in being larger and also in the direction of the enamel folds. This tooth is preserved in the British Museum of Natural History at South Kensington, and I have recently had the opportunity of examining it; but the second tooth I have been unable to discover, concerning which G. R. Waterhouse says it ‘‘scarcely differs from that of the European species ’’.
Richard Lydekker ( Catalogue of Fossil Mammalia in British Museum, pt. i, 1885, p. 221, No. 27985) notices the figured specimen, repro- duces the woodcut, and says ‘‘it comes nearer to the molars of Trogontherium, but does not seem to agree exactly with any specimen available for comparison ”’.
The deposits at Copford, as shown by John Brown, include a comparatively modern deposit, containing many land and freshwater shells, and an underlying blue clay from which remains of ‘‘ Elephant, Stag, Aurochs, Bear, Beaver’”’ were obtained, as well as some fresh- water species of Mollusca. Some geologists seem to have had grave doubts as to the true age of these Copford beds; but at the present time, although there may have been some unfortunate mixing of the shells from beds 2 and 4, there is little room for doubt as to the Pleistocene age of the mammalian remains above-mentioned, nor as to their having been found in the ‘‘ blue clay ’’ marked in the section as ‘‘ Brick Earth”’. |
It was just fifty years after the publication of John Brown’s paper that the giant beaver, Zrogontherium, so commonly met with in the Plocene Forest Bed, was first recognized in the Pleistocene deposits of the Thames Valley (Gror. Maa., 1902, p. 385). Unfortunately when that paper was written I had not studied the Copford ‘ Beaver’, otherwise it might have been included as additional evidence of Trogontherium having survived in this country in Pleistocene times. The original figure does not give a good idea of this tooth on account of the direction in which it is viewed, and the careful drawing given on p. 323 may help toremedy this. The enamel of the posterior margin of the worn surface has been chipped away, but its position is indicated in this figure (@) by a dotted line; also the basal part has been somewhat broken since the original figure was made. This tooth is an upper premolar 4 of the left side, and agrees very closely with that of TZrogontherium Cuviert figured in the Geological Survey Memoir (Vertebrata of the Forest Bed Series, 1882, pl. xi, fig. 15, lowest tooth of the figure). I have no doubt as to its reference to Trogontherium, and it shows no differences by which it might be separated from 7. Cuvieri, in which the patterns of the grinding surface of the teeth vary greatly as they are worn down. The rapidity with which the lateral folds of enamel are worn away so as
R. M. Deeley—LIsostasy. 3238
to leave islands of enamel is one of the chief characters of Trogontherium in which it differs from Castor, and this feature is strikingly shown in the Copford tooth. Although only a com- paratively young tooth, as proved by the narrowness of the grinding surface compared with the remainder of the crown (Figure, 6), the single inner fold (a) extends only 5-5 mm. from the worn surface ; while of the three outer folds (c) the posterior one is already an
Trogonthervum from Copford. Upper premolar 4 from left side. Nat. size. a, inner side, showing one fold of enamel; 6, front surface; c, outer side: arrows point to folds; d, grinding surface, showing enamel folds and posterior enamel island. The enamel at back of tooth has been broken away, and is here restored by dotted line.
island (d@) disconnected from the outer wall of enamel, and the other two are nearly in the same condition, the anterior and largest one being only 1 mm. in depth.
mm. Greatest length of tooth . : : é 28-7 Greatest width of tooth . : ; 12-7 Back to front of tooth . ‘ i ¢ 9-0 Back to front of worn surface . f ; 8-5 Width of worn surface . é i 5 10-0
I have to thank my friend and colleague, Mr. Clement Reid, for the suggestion that I should examine the Copford ‘ Beaver’ and possibly confirm Richard Lydekker’s shrewd perception of its affinity to Trogonthervum. The results of my examination of the specimen are expressed in this note.
VIII.—Isosrasy. By R. M. DEELEY, M.Inst.C.H., F.G.S.
URING recent years the question of the conditions of stress and strain in the earth’s crust has received a very considerable amount
of attention. Perhaps one of the most fruitful limes of inquiry has been that which has aimed at determining the connexion between the varying densities of the crustal rocks and the different degrees of relief of the surface of the earth. It soon became apparent that in mountainous or elevated regions the deep-seated rocks were
324 R. M. Deeley—Isostasy.
of less density than those beneath lowlands and seas, and it became clear that the elevated regions were sustained by the buoyancy of the lighter rocks beneath them. The theory that the earth’s crust was in isostatic equilibrium thus arose.
Careful measurements have shown that a perfect condition of isostatic equilibrium does not exist. Beneath many mountain ranges the deep-seated rocks are often sufficiently ight in character to support mountains of greater elevation than exist above them, whilst in other cases the rocks are not sufficiently dense to support the weights above. In many cases these departures from perfect isostasy are very marked and present considerable theoretical difficulties. Barrell, for instance, concludes that ‘‘Isostasy ....is nearly perfect, or is very imperfect, or even non-existent, according to the size and relief of the area considered ”’.
A very interesting suggestion of Barrell’s is that the more or less rigid rocks of the lithosphere are separated from the rigid materials of the nucleus by a region where the rocks are very soft and allow the lithosphere above to float on it. It is taken to extend from a depth of about 200 km. to 400 km. or more.
Barrell suggests that the reason why the condition of isostatic equilibrium is not more perfect than it is, is that the rocks of the lithosphere are so immensely strong that they are able to act as a girder and support the local excess weights in this way. In support of this he calculates that at a depth of 25 km. the rocks are five times as strong as they are at the surface. It seems very doubtful, however, whether the crust could support in this way some of the immense departures from isostatic equilibrium that are known.
Perhaps the difficulty may be explained in another way. In a mountainous area the action of denuding agents keeps reducing the height of the mountains, and the material thus removed is spread over the neighbouring sea-floor. For a condition of isostatic equilibrium to persist such mountains should rise and the sea-floor be depressed. . For such a change of level to take place there must be a flow of rock in the region of the asthenosphere from below the sea towards the mountains. Now if the rocks of the asthenosphere were liquid, but very viscous, such a flow could readily take place until isostatic equilibrium was reached. On the other hand, if the rocks were plastic, and very soft, such a flow would not be able to occur until the stresses reached some particular magnitude depending upon the plasticity of the rock. In the case of a “liquid the rate of shear is always exactly proportional to the stress producing it; but in the case of a plastic body such flow cannot take place until the stress reaches some particular magnitude depending upon the degree of plasticity of the rock. It thus arises that although the asthenosphere may be of very considerable thickness, the resistance to flow would be very great if the movement had to effect a portion of it, especially if a thousand kilometres or more long. From this it will be seen that perfect isostatic equilibrium is only possible when the astheno- sphere is in a liquid condition.
It is probable that in places where the relief is considerable, and the condition of isostatic equilibrium approaches perfection, the
Reviews—Dr. R. S. Bassler—Bibliographie Index. 325
temperature of the asthenosphere is high and the rocks approach very closely the liquid condition.
It is not generally recognized that the conditions of stress necessary to set up flow in a plastic substance are very different from those required to cause flow in a liquid.
RAV Tews.
T.—Ray S. Basster. Breriograruic InpEX oF AMERICAN ORDOVICIAN anp Siturian Fossizs. Bull. U.S. National Mus., No. 92. 2 vols. Washington, 1915.
IYVHE term ‘‘ American”’ rightly includes the whole of North and South America. Under ‘ Ordovician”’ and ‘‘Silurian”’ are included all formations that lie between undoubted Cambrian and undoubted Devonian. ‘he ‘‘ Fossils” comprise Vertebrates, Inverte- brates, Plants, and ‘Tracks of doubtful origin. The words ‘‘ Bibliographic Index ”’ refer to the bulk of the book, also described as a ‘‘Bibliographic List of Genera and Species”. What a ‘bibliographic list: or index”? would really be is somewhat doubtful : what Dr. Bassler has given us isa list of generic names in alphabetical order, with a list of the specific names in alphabetical order under the genera to which they belong. Under each generic name is given the name of the genotype, but it is not stated how this has been determined. Dr. Bassler has not ventured to fix one for Orthoceras. The generic and specific names are followed by the main references to literature. Then, for the species, come the horizon and localities (some extra-American), but the type-locality is not distinguished. Lastly, the register numbers are given of any type-material of the species in the U.S. National Museum. The references to literature are brought down to the close of 1914, _ except that Schuchert’s ‘‘ Revision of Paleozoic Stelleroidea ” (1915) and Springer’s ‘‘Monograph of Crinoidea Flexibilia’”’ (not yet published) are also indexed. One does not like to quarrel with a good thing; but is there not too much citation of obvious text-books, and indeed of other Indexes, such as S. A. Miller’s well-known work ? This would be all very well if it did not seem occasionally to lead to the exclusion of far more important references. The long list under Caryocrinites, for instance, contains no reference to the classical memoir of L. v. Buch, except by way of the species C. ornatus ; nor does the discussion of this genus and of the allied Strabalocystites in Paleontologia Indica (1906) find mention even under one of the various species. There is a method in this apparently, for under Petalocrinus, instead of quoting Bather’s elaborate study of the genus published by the Geological Society, Dr. Bassler refers only to the abstract report, and even then, not to the Proceedings of the Society, but to the Grotocrcat Macazine; it is only when his new species are indexed that Bather’s paper is referred to. To parody Polonius, ‘‘Though this be method, yet there’s madness in it.” The Gxotocicat Macazine. here unduly favoured, is on more important occasions ignored: Lebetodiscus (Grot. Mac., 1908, p. 550) and
326 Reviews—W. EL. Ford—Dana’s System of Mineralogy.
Edrioaster levis (1914, p. 117) are among names we have failed to find. Brachiocrinus, J. Hall, is another. Per contra Botryocrinites, the name of a series, is quoted as that of a genus. Butsuch slight errors and omissions are almost unavoidable in a first edition.
The ‘‘ Bibliographic List’’ is followed by an alphabetical index of trivial names, showing the genera to which each has been attached. There is also an alphabetical list of generic names only, with page references to the same names arranged under a biological classification. This is useful, but it might have saved the reader’s time had the main systematic position been indicated by a contraction in the main list, as in Sherborn’s Jndex Animalium. The faunal lists which follow must have cost a deal of work, which it is to be hoped will prove warranted by the use made ofthem. The alphabetic list of American Formation names will certainly be most useful, for there are over 700 used in the book. The correlation of the more important among them is displayed in a set of tables, on the same plan as that adopted in KE, O. Ulrich’s ‘ Revision of the Paleozoic Systems”’ (1911).
Geologists and paleontologists will be most grateful to Dr. Bassler for his labours and to the Smithsonian Institution for the publication of this exceedingly valuable aid to research.
IJ.—Dana’s System or Mrinrracoey.
Tuirp APPENDIX To THE SrixtH Eprrion or Dana’s ‘‘SystEM OF Mineratoey’’. By Witiram E. Forp. pp. xiii+87. New York, John Wiley & Sons, Inc.; London, Chapman & Hall, Ltd. 1915. Price 6s. 6d. net.
VERY working mineralogist has a copy of Dana’s great book lying on his table, and would find himself considerably hampered without its aid. Like all books of the kind, as soon as it appears it starts to become out of date. The sixth edition itself was published in 1892, nearly a quarter of a century ago. It is of such a size that frequent revision was difficult, if not impossible; on the other hand, _mineralogy, like other branches of science, does not stand still, but has made steady progress. The difficulty was met to some extent by the issue of appendices, of which the first appeared in 1899 and ‘the second in 1909. The present appendix covers the six years from the beginning of 1909 to the end of 1914, but, as the author points out in his prefatory note, the outbreak of war caused some disturbance in the mail services, and it is possible that some of the publications that appeared towards the close of the year were not received and have therefore not been included. This appendix has been entirely prepared by Professor Ford, who had completed the second appendix after ill-health had compelled his colleague, Professor E. 8. Dana, to relinquish the task in 1906.
As in the previous appendices, the minerals referred to are arranged in alphabetical order, while a classified list of new names is given in the introductory pages. Reference to the volume is therefore exceedingly simple. Altogether 180 new names are included, but the author regards only one-third of them as well established, the
Reviews—Origin of the Diamond. 327
remainder being evidently varieties of previously known species, or, because of the incompleteness of the investigation, doubtful. The introductory pages contain also a list of the principal literature published during the period in question, a special section being devoted to the literature on the subject of X rays and crystal structure, which constitutes the most striking advance of recent years in the method of investigating the structure of crystals. In order to retain the book within moderate dimensions, the information given under each mineral species is. kept as concise as possible, and illustrations are only added in the case of the more interesting species. Under the heading ‘‘ New Minerals” are given a number of incompletely described minerals which are considered to be new, but have not been named. It was not found practicable to re- calculate the angles and other data given, and the particular author's published values were accepted in every instance ; errors creep in so easily that an independent check, as was the practice with the Danas, would have been very valuable.
Mineralogists will feel a debt of gratitude to Professor Ford for taking up the task perforce relinquished by the younger Dana.
Il1.—Oriern or tHe Diamond.
N original and highly interesting paper on the origin of the
diamond, by David Draper and W. H. Goodchild, is to be found
in the Mining Journal for May, 1916. We have not the space to go
into the details of the author’s remarks, but must content ourselves with quoting their conclusions :—
1. A kimberlite pipe does not differ essentially from an ordinary voleanic vent.
2. The lava is derived from an infra-granitic zone basaltic in character, eclogite, but the original lava is not necessarily either . ultra-basic or highly peridotitic.
8. Minute diamonds may be present invariably as an accessory mineral in the eclogite from which the pipe material is derived, but the evidence on this point is inconclusive.
4, Towards the end of the active period of vulcanicity differentia- tion of the magma in the vent is brought about by the sinking of early formed crystals, principally olivine and ferro-lime pyroxenes, thus producing an ultra-basic mass in the lower regions of the vent. The ultra-basie character of kimberlite is thus due to magmatic differentiation, and not to a primary derivation from an ultra-basic source.
5. After freezing of the magma in the upper regions of the vent, the molten residuum beneath the solid plug continues to be slowly impregnated with magmatic gases, chiefly water and carbon dioxide, thus hydrating the melt, lowering its viscosity, and prolonging the solidification period, and at the same time effecting extensive serpentinization. The serpentinization is thus due to a solution of carbon dioxide in water under pressure and introduced from below, and is not the result of weathering by downward percolating solutions.
328 Reviews—The Nitrate Shales of Egypt.
6. During this period a process somewhat analogous to secondary enrichment occurs, resulting in the growth of larger diamonds at the expense of minute crystals.
7. The economic diamond is therefore to be regarded as essentially a secondary mineral grown in situ in the kimberlite matrix.
IV.—Tue Nirrare SHatzs or Keypt. By Dr. W. F. Home, Assoc. R. C. Sci., F.G.S., Director Geological Survey of Egypt.
N Mémoires de l'Institut Egyptien (1915, vol. viii, pp. 145-69) Dr. W. F. Hume summarizes the work in connexion with the nitrate shales of Egypt. Generally they have yielded on analysis 5 per cent or less of sodium nitrate. The difficulty in their commercial development has been caused by their variability in distribution. They are present at a definite horizon in the geological series, forming part of the uppermost Cretaceous strata (Esna Shales and Ashgrey Clays), and have been traced from Farafra Oasis to West Sinai. Their wide distribution at the same horizon suggests that they represent compounds formed or absorbed at the time of deposition of the shales; on the other hand, the presence of sodium nitrates being only marked near the surface suggests that they are either formed by some means now acting, such as nitrifying organisms working under moist conditions of the soil, or have been drawn to the surface by capillarity.
V.—Geotocicat Survey or New ZEALAND.
Burtetin No. 17, New Series, or tHE GeotocicaL Survey or New Zeatanp. By P. C. Morgan and J. A. Bartrum. pp. vui-+ 210, with 19 plates, 18 figures, 9 maps, and 6 geological sections. Wellington, 1915.
f}\HE authors give an exhaustive account of the geology and
mineral resources of the Buller-Mokihinui Subdivision, Westport Division, which district lies on the west coast of the South Island. The mining industries include gold-mining, mainly alluvial, which was at one time very prosperous, but is now almost extinct, coal- mining, and to a small extent rock-quarrying. ‘he supplies of coal, particularly the bituminous variety, in New Zealand are very limited, and will probably approach exhaustion in at the most one hundred and fifty years. The bituminous coal as yet known is contained almost wholly in the Greymouth and Westport Districts. The authors call attention to the loss of coal resulting from the methods of working it. The geological formations consist of two sets separated by a striking unconformity: the one is composed of highly folded grey wacke, argillite, hornfels, schist, gneiss, and intrusive acid igneous rocks, which were base-levelled in pre-Tertiary times, and on this peneplain was deposited the second set of strata, consisting of a succession of breccias, conglomerates, grits, sandstones, mudstones, and limestones, in places unconformably capped by Quaternary sands and gravels. The Bulletin is excellently illustrated.
~ Reviews—Eocene Glacial Deposits in S.W. Colorado. 329
VI.—Eocene Gracrat Deposits 1x Sourn-WeEsTERN Cotorapo. By W. W. Arwoop. U.S. Geol. Surv. Prof. Paper No. 95 B, 1915, pp. 11-26, with 4 plates.
VERY addition to the growing list of pre-Pleistocene glaciations is of interest, and Mr. W. W. Atwood gives conclusive evidence for the occurrence of an Eocene Boulder-clay on the plateau of South- Western Colorado. In his study of this deposit he has been aided by a party of advanced students from Chicago University. This Eocene Boulder-clay is situated a mile west of Ridgeway, N.N.W. of the mining field of Ouray, at about 7,800 feet above sea-level. It occurs near Pleistocene glacial deposits. The Eocene Boulder-clay rests upon a wide sheet of Mancos Shale; it consists of a layer, about 100 feet. thick, of yellowish till containing a great variety of boulders, including igneous and sedimertary rocks which range from the pre-Cambrian to the Upper Cretaceous. The boulders range up to 5 feet in diameter; they are faceted, and a large proportion are striated. The Boulder-clay is covered by a slate-covered clay con- taining a few very small pebbles, and this bed is also regarded as a till. Above it rest the Telluride conglomerates and the San Juan tuffs, which are well known from their connexion with the ore deposits of Colorado. ‘lhe evidence seems conclusive both as to the glacial origin and Eocene age of this deposit, but as Pleistocene glacial beds also occur in the same neighbourhood, and as the Kocene in this district was a period of mountain uplift, this Boulder-clay is an indication of a mountain glaciation and not of any widespread glacial climate.
VII.—Grotoeica, SurvEY oF PorruGAt.
VHE yearly volume of the Geological Survey of Portugal contains ; several interesting papers (Commun. d. Comissao do Serv. Geol.
de Portugal, tom. x, 1914). P. Prevost, in writing on the Devonian and Carboniferous of Portugal, demonstrates the presence of all stages of these formations save the Middle Devonian. This paper contains the description of a new species of Goniatite (Prolecanites algarbiensis) from the Culm of Aljezur. V.Sousa-Brandao describes at length a universal mineralogical microscope on a new model. The same author also describes ‘‘ porphyroblastic phyllites”? from the Pre-Cambrian of Aveiro. These are divided into staurolite-garnet- phyllites, staurolite-phyllites, and chloritoid-phyllites, which are treated in detail. A supplementary paper describes the optic orientation of the chloritoid in the above-mentioned rock. Economic geology is represented by two papers by P. Choffat, who summarizes the evidence for the occurrence of petroleum in the Mesozoic region of Estremadura, and describes the history and geology of the garnet mines of Suivo which were worked by the Romans. The gems occur in a basaltic breccia. The final paper is a valuable bibliography of the geology of Portugal and its colonies in 1913, by P. Choffat and K. Fleury, which is the eleventh contribution of a similar nature.
G. We
330 Reports & Proceedings—The Royal Society.
REPORTS AND PROCHEHDIN GS.
I.—Tue Royat Socrery. June 1, 1916.—Sir J. J. Thomson, O.M., President, in the Chair.
A paper was read by Mr. E. A. N. Arber, Sc.D., ‘‘On the Fossil Floras of the Coal Measures of South Staffordshire.”” (Communicated by Professor McKenny Hughes, F.R.S.)
A flora of fifty-eight species is described from a new horizon in South Staffordshire, the Red Clay series or Old Hill Marls of Transition Coal-measure age. A new genus Calamophlotos and new species of Sphenopterits and Cardiocarpus are described, as well as several records new to this horizon.
Ten new records are added to the known flora of the Productive Series (Middle Coal-measures), including new species of Calamites and Leprdostrobus. A large number of additional records from new localities or horizons are added in respect te fossils already known from these beds.
II.—Groxrocicat Socrery or Lonpon. 1. May 24, 1916.—Dr. Alfred Harker, F.R.S., President, in the Chair.
Dr. A. Smith Woodward, F.R.S., V.P.G.S., exhibited Devonian fish-remains from Australia and the Antarctic regions, and discussed our present knowledge of the Devonian fish fauna of the southern hemisphere. So far as is known, there are no strange elements in this fauna, and the remains discovered closely resemble those met with in the Northern Hemisphere. Even the rocks are very similar to those containing the corresponding fossils in the Northern Hemisphere. ‘There is, as yet, no satisfactory evidence of the basal Devonian fish fauna such as occurs in the Downtonian of England and Scotland ; but both Lower and Upper Devonian forms occur in Victoria and New South Wales (Australia). A Coccostean related to Phlyctenaspis from Gippsland (Victoria), and another related to Macropetalichthys from Goodra Vale (New South Wales), may be regarded as Lower or Middle Devonian; typical plates of Bothriolepis from the Harvey Range (New South Wales) indicate an Upper Devonian fauna. he fish-remains obtained by the Discovery Expedition in Granite Harbour (Antarctica) comprise Bothriolepis, another Ostracoderm related to Byssacanthus, Acanthodian scales, Selachian dermal tubercles, a Coccostean, scales of Osteolepide, and scales of a very small Paleoniscid. They must be regarded as Upper Devonian.
Dr. Woodward expressed his indebtedness to the Government Geologist of New South Wales for the loan of the Australian specimens exhibited. ;
Mr. R. Bullen Newton exhibited some so-called Orbitoidal Limestones from Dutch New Guinea, the microscopical structures of which were shown by lantern illustrations. The specimens were collected by Dr. A. F. R. Wollaston during his expedition to that country in 1912-13, on the snow-line of Mount Carstensz at a height of 14,200 feet, this mountain forming the highest elevation of New
Reports & Proceedings—Geological Society of London. 331
Guinea, with an altitude of about 16,000 feet. The foraminiferal organisms determined in this material included five species of Lepidocyclina (sumatrensis, martini, neodispansa, murrayana, and ct. insule-natalis), Amphistegina, Carpenteria, Cycloclypeus (cf. orbitordeus), etc.; the marine alga or nullipore, Lithothamnium, was, also, largely represented. This assemblage compares favourably with that which characterizes rocks of similar age in other Pacific regions, such as Christmas Island (Indian Ocean), Formosa, the Philippines, Borneo, Celebes, Sumatra, Nias, Timor, Australia, besides indicating a Miocene origin. It was pointed out that the genus Orbitordes of A. @’Orbigny had been restricted by Schlumberger (relying on the researches of Giimbel, Verbeek, and others) to species having rhomboidal equatorial chambers and belonging only to Cretaceous times; species furnished with rectangular chambers, and recognized as Orthophragmina of Munier-Chalmas, were limited to the Kocene - and Oligocene formations; while Giimbel’s genus Lepzdocyclina, with rounded or hexagonal chambers, included species of Miocene and later age. As the result of a study of species from Borneo and the Philippines, Professor Douvillé had proposed to divide Lepidocyclina into two sections—Hulepidina and Nephrolepidina: the first including forms of generally large size, recognized as Aquitanian; the second for those of small dimensions, regarded as Burdigalian—these geological divisions representing the oldest stages of the Miocene system. This distinction, however, was not applicable to the New Guinea limestones nor to corresponding rocks from Christmas Island, as both large and small species occurred in association; it was therefore suggested that the age of the New Guinea material might _ be referable to the later part of the Aquitanian. Several writers have already written on rather similar limestones from various parts of New Guinea, although we are indebted to Dr. K. Martin for the first announcement in connexion therewith : he reported the discovery in 1881 of Lepidocycline organisms from rocks found in the north and south-western end of the country (Geelvink Bay, islands of Kei, Aru, etc.), which he attributed to the older Miocene. The same author also referred to the occurrence of similar organisms in Mount Wilhelmina, obtained by Dr. Lorentz, beneath which the Alveolina Limestone was identified, proving the existence of Hocene rocks.
The Cycloclypeus remains, which are of frequent occurrence in the present material, bear a strong resemblance to Professor Douvillé’s new genus and species from the Miocene of Borneo, known as Spiroclypeus orbitocdeus. This genus was stated to have all the characters of Cycloclypeus, but differing from it in the possession of superficial chamberlets in the shelly layers of the central region. Recent investigations, carried out by the speaker, had proved the presence of this character (hitherto unrecognized) in modern forms of Oycloclypeus from Funafuti; hence the retention of Sprroclypeus now appeared to be unnecessary. A full report on this New Guinea collection by the speaker had been lately published, entitled ‘‘ Notes on some Organic Limestones, etc., collected by the Wollaston Expedition in Dutch New Guinea’’—forming No. 20 of a series of reports, and it was to be included in vol. 11 of those reports.
332 Reports & Proceedings—Geological Society of London.
2. June 7, 1916.—Dr. Alfred Harker, F.R.S., President, in the Chair.
Dr. F. L. Kitchin, M.A., F.G.S., exhibited a representative set of Mesozoic fossils obtained from deep borings and pit-sinkings in Kent. The specimens were selected from the collections of the Geological Survey, by permission of the Director. The life of the successive zones present in the various sections was illustrated by the arrange- ment of the specimens in sequence, the series comprising a time-range from the Lower Lias up to the top of the Lower Greensand. The ‘section revealed in the Brabourne boring is remarkable for the range of formations found there in superposition, and may be regarded as the type-section for the study of the hidden Mesozoic succession in Kent. Specimens were exhibited from that locality and from the shafts at Dover, but these were supplemented by materials obtained more recently from various borings situated east of a line drawn from Folkestone to Canterbury.
The speaker described the principal characters of the faunas as developed in this area, and made incidental references to the nature and distribution of some of the associated rock-types. At some horizons the molluscan assemblage assumes a particular aspect by reason of the preponderance of species fitted for life amidst the special conditions of deposition. On the other hand, there are evolutionary phases which recur repeatedly with considerable uniformity, and seem to arise independently of immediate sur- rounding conditions. Such are illustrated by the degenerative changes shown to occur in many Ammonites, and by some of the forms repeatedly assumed by the members of separate series among Mesozoic oysters.
The evidence of Ammonites, so important for the purpose of zonal determination, is frequently forthcoming at these localities in Kent, even in borings of narrow diameter, but it is often necessary to rely entirely upon the aid afforded by the more abundant bivalves. Many of these, although belonging to undescribed species, are found to have a limited vertical range, and by their distribution throughout this area, as well as farther afield, prove of much service in these correla- tion studies. Specimens of many undescribed species have come to light, as well as others which are known from their occurrence in Continental localities, though not previously recorded in this country.
A small series of Jurassic Cephalopoda from Kachpur (Russia), collected by the late G. F. Harris, F.G.S., at the time when the . International Geological Congress met at Petrograd (1897), was exhibited by James Francis, F.G.S.
III.—-Zooroeicat Society or Lonpon. 1. May 9, 1916.—Dr. 8. F. Harmer, M.A., F.R.S., Vice-President, in the Chair.
Miss Dorothea M. A. Bate contributed a paper dealing with a collection of vertebrate remains from the Har Dalam Cavern, Malta. Birds are most numerously represented therein, and include some bones of an Anserine bird showing a reduction in its powers of flight. It is believed to be a hitherto undescribed species, and is
referred to the genus Cygnus. A list is given of all the species of
Reports & Proceedings—Zoological Society of London. 333
vertebrates recorded from the Pleistocene cave and fissure deposits of the island.
2. May 23, 1916.—Dr. Henry Woodward, F.R.S., Vice-President, in the Chair.
The Rev. H. N. Hutchinson, M.A., F.Z.S., exhibited the plaster cast of a model, four feet long, which he had constructed of the Dinosaur, Diplodocus carnegier.
Lieut. R. Broom, M.D., C.M.Z.S., R.A.M.C., read a paper on the structure of the skull in Chrysochloris.
Two stages in the development of the skull have been studied. The earlier is that of a newly born Chrysochloris hottentota, whose skull has been cut into microscopic sections and reconstructed, and a somewhat later stage of Chrysochloris asiatica, whose skull has been prepared for the study of the membrane-bones. The following are the most interesting features discovered :—
External to the exoccipitals on each side is a large membrane-bone which partly covers the petrosal or periotic. This is believed to be the homologue of the bone which occurs in Therapsid and most primitive reptiles, and usually referred to as the tabular. The sections prove that it is no part of the auditory capsule.
Along the inner side of the prearticular or ‘‘ goniale ’’—the little membrane- bone which supports the underside of the upper end of Meckel’s cartilage—is a second membrane-bone, which, it is believed, has not been previously recognized in the mammal skull. This may be the homologue of the reptilian surangular.
_ Under the back part of the nasal capsule, and situated between the _ capsule above and the alisphenoid and pterygoid below, is a large membrane-bone of doubtful significance. It is probably the homologue of the ‘ postero-lateral vomer’’ of Parker.
The skull is held to be in some respects highly specialized and in . others degenerate, although also retaining a number of very primitive characters.
Dr. C. W. Andrews, F.R.S., F.Z.S., described an incomplete sternum of a gigantic carinate bird from the (?) Kocene of Nigeria. Comparison with the sterna of several groups of birds leads to the conclusion that this specimen, though differing considerably from the sternum of any living member of the group, belonged to a very large representative of the Tubinares. It has about twice the linear dimensions of the sternum of an Albatross, of which the spread of Wing (in the flesh) was 10 ft. 8in. It is proposed to refer this species to a new genus Gigantornis, the specific name being G. eaglesomet after its discoverer.
Dr. A. Smith Woodward, F.R.S., V.P.Z.8., read a paper on _ amammalian mandibular ramus from an Upper Cretaceous formation in Alberta, Canada. ‘The specimen represented an opossum-like marsupial, and he referred it to a new species of Cimolestes named C. cutlert in honour of its discoverer, Mr. William E. Cutler. The close dental series behind the canine measured 30 mm. in length, and the molars differed from those of the two known species of the genus in their relatively less elevated trigonid. The fourth premolar was
334 Reports & Proceedings—Geologists’ Association, London.
a large, tumid, laterally compressed cone, with one well-separated posterior cusp.
IV.—Geotoetsts’ Association, Lonpon. June 2, 1916.—George Barrow, Esq., F.G.S., President, in the Chair.
The following paper was read: ‘‘The Petrology of the North Sea Drift and Suffolk Brick-earth.” By Perey G. H. Boswell, D.Sc., F.G.8., A.R.C.S.
1. The varied facies of the North Sea Drift and Suffolk Brick-earths. Mechanical analyses; graphical representation of results; economic values; comparison with other British deposits.
2. Petrography. Detrital residues and comparisons with residues from other glacial beds.
The paper was a sequel to that published by the Geological Association in 1913, dealing with the field evidence which served to distinguish the North Sea Drift (Lower Glacial) from the Brick- earth of Suffolk (Upper Glacial).
The three facies of the North Sea Drift, (a) the Cromer Till, etc., of the coast sections, (b) the Marly Drift of the Western area, and (c)the inland Norwich Brick-earth, were briefly considered. Mechanical analyses were given of the deposits, and expressed graphically by means of curves. The Lower and Upper Glacial deposits were shown to conform to very different types, pointing to different modes of genesis. They could easily be distinguished from one another by grade composition.
Although small variations in mineral composition occurred, the Upper and Lower Glacial Brick-earths did not each possess a distinctive and differing mineral assemblage. As would be expected from the varied sources of their constituent materials, the glacial deposits generally yielded an exceedingly rich and beautiful assemblage consisting of over forty mineral species, many of which were derived directly from the breaking up of fresh igneous rocks. The most abundant detrital minerals included garnets, epidotes, hornblendes, ‘and pyroxenes (soda-bearing varieties included), hypersthene, micas, staurolite, kyanite, andalusite, apatite, and others.
A lecture was also delivered (illustrated by lantern views) entitled ‘Notes on Erosion Phenomena in Egypt ’’, by Miss Mary S. Johnston, F.R.G.S.
Amongst other phenomena of erosion the lecture illustrated the decomposed igneous rocks at the Second Cataract, and the pot-holes and shade-weathering in the granite of the First Cataract. The variation in the constituents of the Nubian Sandstone, the rivers of blown sand on the west of the Nile, and the famous quarries of Gebel Silsileh were described. Reference was made to interesting geological features of the Theban mountains, notably the Eocene chert concretions, and the dry river-valleys and gravels. The significance of certain sites from which numerous worked flints have been collected were also considered and illustrated by views and specimens. The action of the sun, wind, and water upon the Mokattam limestones was referred to in connexion with the formation of Wadi Hof and the production of the etched surface of the Sphinx.
Reports & Proceedings—Geological Society, Glasgow. 335
Fine specimens of split and eroded cherts from Oligocene gravels were shown.
V.—GerotoeicaL Socrery, Grascow.
At a meeting of the Geological Society of Glasgow on May 11, 1916, Mr. Macnair exhibited a series of specimens got from the ancient bed of the Clyde in the course of digging the foundations of the new Dalmarnock Power Station. The specimens consisted of hazel-nuts, twigs and timber, and the epidermis of pearl mussels. The pearl _ mussels had lost all trace of their calcareous shells through the action
of percolating water, and only the chitinous epidermis remained, resembling dead leaves in brittleness and form. He pointed out that the occurrence of such relics had been recorded about half a century ago 1n proximity to the present course of the Clyde, and there could be no doubt that they came from the same bed which also contained human relics in the shape of dug-out canoes.
Professor J. W. Gregory read a paper on ‘‘ The Auld Wives’ Lifts: a Pseudo-Megalithic Tor’. He described the position of the well- known stones and referred to the traditional explanation of their
origin, which ascribes them to a trial of strength between three witches of the district. For long the stones have been regarded as an example of a cromlech erected by the race which has dotted the country with megalithic structures. Careful examination, however, has shown that the group is purely the result of natural processes of denudation isolating a portion of the gritty sandstone of the district which had been dismembered and the fragments thrown into their present attitude by slipping along joints and bedding planes. It was shown that this could be proved by the fact of the existence of the lines of fracture of prominences corresponding with hollows on the opposite block. ‘
Mr. Ludovic McL. Mann pointed out that although the erection of the blocks could not be ascribed to man and the structure differed in ' some respects from the typical cromlech, there could be no doubt that it had been adopted by the early inhabitants of the district. He believed that the upper surface of the capstone had been levelled by the prehistoric process of ‘ knapping’ and had then been sculptured, the traces being quite evident to the trained eye. Other evidence also showed that the district had been one of special interest to the early inhabitants and was now of importance to the archeologist.
VI.—Mrnzratoetcan Sociery.
June 20.—Dr. A. E. H. Tutton, F.R.S., Past-President, in the Chair.
Dr. J. W. Evans: The Relations between different Laws of Twinning giving the same Twin-crystal. If the untwinned crystal has no symmetry, different twin-laws give different results. In the presence of a centre of symmetry an axis of rotation-twinning is an axis of reflection-twinning. An axis of rotation-twinning lying in a plane of symmetry has at right angles to it in the same plane an axis of reflection-twinning. If the normal to a plane of symmetry be an axis of rotation-twinning, or if a line of symmetry (axis of even symmetry) be an axis of reflection-twinning, the same result may be
336 Reports & Proceedings—Mineralogical Society.
obtained by the complete inversion of the structure; vice versa, in an inversion-twin the normal to every plane of symmetry is an axis of rotation-twinning, and every line of symmetry is an axis of reflection-twinning. If a twin-axis be at right angles to an axis of nm degrees of symmetry, there will be in all » twin-axes of the same kind at right angles to the same axis of symmetry. Other more complex relations were described.—Dr. G. T. Prior: The Meteorites of Khairpur and Soko-Banja. The Khairpur meteorite is precisely similar to the Daniels Kuil, and like it belongs to the rare Hvittis type of chondritic stones, which contain oldhamite, and are almost free from oxide of iron. The Soko-Banja meteorite contains a small amount (4 per cent) of nickel-iron, very rich in nickel, together with ferro-magnesian minerals, rich in ferrous oxide. —Dr. G.'l’. Prior: On the Classification of Meteorites. In chondritic stones the richer the nickel-iron in nickel the richer the ferro- magnesian minerals in ferrous oxide, and in general the smaller the amount of nickel-iron the richer it is in nickel. On these principles chondritic stones are divided into four groups, corresponding to the types: (1) Daniels Kuil, (2) Cronstad, (3) Baroti, (4) Soko-Banja. Under the same groups the meteoric irons may be arranged according to their richness in nickel, and the non-chondritic stones according to the richness in iron of the ferro-magnesian silicates, except that a fifth group is added for Eucrite, Howardite, Shergottite, Angrite, and Nakhlite, since they are richer in lime, ferrous oxide, and mostly also in alumina than any chondritic stone at present known.— Lieutenant A. Russell, R.E.: Note on a new occurrence of Gold from Cornwall. Alluvial gold was found in the bed of a small stream adjoining a jamesonite mine near Port Isaac.—A. Holmes: On aseries of Volcanic Rocks from the neighbourhood of the Lucalla River, Angola. The rocks described were collected by J. J. Monteiro in 1860, and include porphyritic basalts, biotite trachyte, trachyte with xgirine and cossyrite, nephelinite, and pyroxene andesite. They occur partly over Archean and partly over Karoo rocks, and are probably related to the Vertiary alkali rocks between Senza do Itombe and Bango. An olivine camptonite of post-Miocene age from Dombe Grande, near Benguella, was also described.—Professor T. L. Walker: Spencerite, a new Zine Phosphate from British Columbia. The new mineral occurs as the core of stalactites of hemimorphite in the H.B. zine- mine near Salmo in the West Kootenay district. It is snow-white in colour with brilliant pearly lustre on the perfect cleavage. The three rectangular cleavages and the optical characters suggest at first sight rhombic symmetry, but complex lamellar twinning is present, and etched figures are symmetrical about one plane only. Analyses of the very pure material conform closely with the formula Zn3. (PO4)2 . Zn (OH), . 3H, 0, the mineral being a hydrated basic zine phosphate, and thus differing from the other zine phosphates— hopeite, parahopeite, and tarbuttite. It is named after Mr. L. J. Spencer, of the British Museum.—E. L. Bruce: Magnesian Tourma- line from Renfrew, Ontario. Brown crystals occur at the contact of crystalline limestone and gneiss in a limestone quarry at the town of Renfrew. Analysis shows the presence of 14°58 per cent of magnesia.
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_ THE FLOWERING PLANTS OF AFRICA |
©. AN ANALYTICAL KEY TO THE ‘GENERA OF 7 AFRICAN PHANEROGAMS.
BY
FR. THONNER.
XVI and 640 Pages, 150 Plates, | Map. — Cloth.
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Re oe GHOLOGICAL MAGAZINE
NEW SERIES. DECADE VI. VOL. At gonian instip
No. VIII.—AUGUST, 1916. ES
ORIGINAL ARTICLE
——»—__——
I.—NotkEs oN NEW OR IMPERFECTLY KNOWN CHALK oi Piea| Musee By R. M. Bryponez, F.G.S. oped (Continued from the June Number, p. 243.) PLATE XIV. MeMBRANIPORA FASCELIS, sp. nov. (Pl. XIV, Figs, 1, 2.)
Zoarium unilaminate, adherent.
Zoecia fairly large, with very little external front wall; areas widely elliptical, flattened for a short way at the upper end and surrounded by a slender rim, average length -5 mm., breadth -35 to -4mm.
Oecia very constant in occurrence, semicircular in plan, borne on the very scanty front wall of the succeeding zoccium and often impinging slightly on its area.
Avicularia very numerous, nearly always small and interstitial, but occasionally (Fig.2) large and vicarious or sub-vicarious, very unifor mly well preserved ; they are of hour-glass type, short and wide, and the ends of a crossbar occur about one-third of the way up the aperture; these ends are so sharp and uniform as to suggest that they are not the remains of a broken calcareous bar but the well-preserved supports of a membranous bar.
This species occurs sparingly in the zone of UW. cor-anguinum in Hants and Kent; and I have a dwarfed specimen from the zone of Marsupites in Hants. It seems to form a lineal series with the three following.
MeEMBRANIPORA FAUSTINA, sp. noy. (Pl. XIV, Fig. 3.)
Zoarium unilaminate, adherent.
4oecia large, shallow, and entirely devoid of front wall, which gives them a very primitive appearance, very variable in shape, and often developing a long narrow handle at the lower end which in a less primitive form would be a very probable mark of avicularia; *6 mm. would perhaps be a fair average length of area, apart from the handle-like extension which may add almost any length to the zoecia in which it occurs ; at the lower end there is very regularly developed a crescent-shaped to semicircular cavity in the floor which may be ocecial in nature.
Oecra do not occur.
Avicularia numerous, of the same general type as those of M. fascelis, but smaller and in proportion much narrower; they are
DECADE VI.—VOL. III.—NO, VIII. : 22
338 R. M. Brydone—New Chalk Polyzoa.
always interstitial and sometimes impinge sharply on the adjoining zocecia.
This species occurs in the zone of JL. cor-testudinarium in Hants, and probably in those upper beds which for Dr. Rowe are the lower fourth of the zone of If. cor-anguinum. Ihave only one specimen, and should not have described it but for its apparent serial relation- ship to JL. fascelis.
MemBraNIPORA FERONIA, sp. nov. (Pl. XIV, Fig. 4.)
Zoartum unilaminate, adherent.
Zoecia definitely pyriporiform, with a long and generally very ~ slender tapering external front wall; areas narrowly elliptical, average length 45 to ‘5 mm., breadth -27 mm., separated from the external front wall by a slender but definite rim.
Oecia wide and slightly heel-shaped in ground-plan, not numerous.
Avicularia much like those of JZ. fascelis, even to the occasional vicarious specimens, but smaller, and in proportion much narrower, and placed centrally above the zocecia as a rule; the crossbar is undoubtedly calcareous, being frequently preserved ; it divides the aperture into two nearly equal parts, the upper being slightly the _ larger.
‘his species is rare in the zones of A. quadratus (restricted) and B. mucronata in Hants. It closely resembles Keptoflustrella ovalis, D’Orb.,! the only clear distinction lying in the avicularia, which in R. ovalis are smaller, quite different in shape, and devoid of any suggestion of crossbar; but the resemblance can only be accidental if Canu is right in identifying the latter species with Semeflustrella rhomboidalis, D’Orb.,? which is palpably distinct from JL. feronia.
MeEMBRANIPORA FLACILLA, sp. nov. (Pl. XIV, Fig. 5.)
Zoarium unilaminate, adherent.
Zoecia feebly pyriporiform, with very short and rapidly tapering - external front wall; areas distinctly large, length °55 to *65 mm., breadth °38 to'4 mm., elliptical and definitely flattened at the upper end, and separated from the external front wall by a faint rim; just outside the two corners formed by the flattening of the upper end a pair of pores occurs very regularly in a swelling of the rim.
Oewcia broad and slightly heel-shaped in ground-plan, fairly numerous.
Avicularia corresponding almost exactly with those of IL feronia; the ends of the crossbar are about half-way up the aperture.
‘This species is rare in the Weybourne Chalk (zone of B. mucronata), and is apparently the last of the English series, as I have not met any representative in the Trimingham Chalk.
MEMBRANIPORA FLAMMIA, sp. nov. (Pl. XIV, Figs. 6, 7.)
Zoartum unilaminate, adherent. Zowcia rather small, the initial zocecia of new rows feebly pyri- poriform, more as it were of necessity than by choice; areas in the
1 Pal. Terr. Crét. Franc., v, p. 571, pl. 731, figs. 17, 18. 2 Thid., p. 564, pl. 730, figs. 5-8.
PLate XIV.
Geo-. Mae., 1916.
R.M. Brydone, Photo.
< S) N i fe) a x“ dl q = O
Dr. Marr & M iss Gardner—Pleistocene Beds, Barnwell. 339
early stages slightly oval, but in the later stages often truly elliptical, and ranging in length from °35 to °5 mm.
Owcia very abundant, borne upon a scanty front wall provided by the succeeding zoecium at the expense of a broadening and flattening of the lower end of its area, which emphasizes, if it is not indeed the sole cause of, the oval shape; they are globular with a definitely concave free edge, but in the later stages the ground-plan tends to become narrowly heel-shaped.
Avicularia vicarious, of hour-glass type, but much elongated and in the lower part rather expanded and inflated; the remains of the
crossbar occur about one-third of the way up the aperture, and apparently spring. from the infolded walls at the lower point where they reach the aperture at which they cause a slight constriction of its “apparent outline; there is a faint tendency “to a similar con- striction at the corresponding upper point.
This species occurs sparingly in the (restricted) zone of A. guadratus in Hants. It seems rather isolated.
MermBRANIPORA FLORA, sp. nov. (Pl. XIV, Figs. 8, 9.)
Zoartum unilaminate, adherent.
Zoecia rather small, with thick areal margins rising out of acommon crust ; areas broadly to narrowly elliptical, average length °35 to -4:mm., breadth -18 to ‘28 mm.; the areal margins bear three or four pairs of perforated tubercles.
Oecia globular, with fairly wide aperture and deeply concave free edge.
Avicularia abundant, interstitial, small sig eirliee with calcareous crossbar, a good deal tilted up on the lower end.
ane bits species occurs sparingly in the zone of IL. cor-testudinarium at
Seaford. The tilted-up avicularia are somewhat suggestive of affinity
with the group of which JL. cuculligera, Bryd.,' is a typical member.
EXPLANATION OF PLATE XIV. (All figures x 12 diams.)
E> | H
CAAP ww H,
Membranipora fascelis. Zone of M. cor-anguinum. Gravesend. M. faustina. Zone of M. cor-testudinarwm. Basing, Hants.
M. feronia. Zone of A. quadratus (restricted). Shawford, Hants. M. flacilla. Zone of B. mucronata. Weybourne.
M. flammia. Zone of A. quadratus (restricted).. Shawford, Hants. M. flora. Zone of M. cor-testudinarwwm. Seaford.
(Zo be continued.)
=
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~
Il.—On some Deposits conrarniné aw Arctic Flora In THE PLEISTO- cENE Beps oF BarnweEtt, CamMsBripGE. By J. HE. Marr, Se.D., F.R.S., and Miss E. W. GARDNER, Harkness Scholar, Newnham College, Cambridge.
NE of us has been engaged for some years in the aids of the Pleistocene gravels and associated deposits of the Cambridge. district, and eventually proposes to give a full account of the results obtained. Meanwhile, considering the importance of noting the
- 1 Gmon. MaG., 1914, p. 481, Pl. XXXV, Figs. 1, 2.
340 Dr. J. FE. Marr & Miss LE. W. Gardner—
conditions under which Pleistocene floras are preserved, in order to draw attention to their probable occurrence under similar conditions elsewhere, it is thought advisable to give a preliminary account of the discovery of an Arctic flora of this date in a pit at Barnwell, a suburb of Cambridge, long noted for its Pleistocene deposits.
The pit in which the plant-seams are exposed is situated to the west of the railway, close to Barnwell Station. The section in this
pit was described and figured by the late Mrs. McKenny Hughes in the |
GuotocicaL Macazine for 1888 (Dec. III, Vol. V, pp. 194-6), and the figure is reproduced with slight alterations in Professor Hughes’ recently published paper, ‘‘ The Gravels of East Anglia”? (Cambridge University Press, 1916). The section has been much enlarged in the last few years, and at present there is a continuous exposure with a length of about 500 feet along the north pit-face in a direction nearly east and west, that is, at an angle of about 45° to the section given in Mrs. Hughes’ paper.
Along this line of section the beds are very even and approximately horizontal, thus showing a contrast to the unevenly bedded deposits figured in the papers cited. These uneven beds are still seen in a face nearly at right angles to the present long face. In this shorter face the base of the deposits is seen to rise towards the south, that is, in the direction of the Newmarket road.
The even- and uneven-bedded deposits belong to the same series, and indeed the one set passes into the other. The uneven-bedded set was deposited against a slope, and where the bedding becomes more even, indications point to deposition on a flatter floor.
The following section is a representation of the beds towards the | western end of the north face. It is in this part of the face that the peaty seams are most abundant and the bedding most even. The section shows clearly that the peaty seams are part of the Pleistocene strata and not deposits of later date banked up against them. The section as figured is about one-tenth of the length of the whole northern face along which the beds are now clearly seen.
The gravels are not very coarse, and some sand beds are seen among them. The loams vary in coarseness, some being sandy, others more clayey. The peaty bands, varying in thickness from one-eighth to half an inch, consist of loamy peat, from which good specimens of leaves, seeds, etc., are readily extracted. Where best developed there are at least five layers of these seams seen in vertical section. The plants hitherto obtained were extracted from the most persistent seam, which is the lowest but one. The section shows the manner in which the various seams die out laterally.
We obtained abundant leaves of a plant which we regarded as Betula nana, and Mr. Clement Reid, F.R.S., who kindly examined our plants, has confirmed this, and in a preliminary list has noted the presence of several additional Arctic forms. There is therefore no doubt that we have here another addition to the Pleistocene Arctic beds of this country.
We do not propose to discuss at present the relationship of this low-level series of deposits to the other Pleistocene accumulations of the district, but content ourselves with stating that their mode of
341
Pleistocene Beds, Barnwell.
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342 Dr. Marr & Miss Gardner—Pleistocene Beds, Barnwell.
occurrence, quite apart from the low level, which is in itself of no great significance, is in favour of their reference to one of the latest, | if not the latest stage, of the Pleistocene deposits of the district.
In addition to the plants the peaty seams have furnished several remains of insects, and-the following shells, which are all of species — recorded by Mrs. Hughes from the beds of the pit: Planorbdis sprrorbis, Succinea oblonga, Helix hispida, and Pupamarginata. Others will no doubt be added when the deposits are worked in greater detail.
No mammalian bones have yet been found in the peaty material, but Mrs. Hughes records Cervus elaphus, Elephas primigenius, Equus caballus fossilis, and Rhinoceros leptorhinus or tichorhinus from the pit. We have recently obtained the horse, the mammoth, the reindeer (Cervus tarandus), and an ilium of Rhinoceros tichorhinus. These were determined by Mr. C. E. Gray, the First Attendant in the Sedgwick Museum. We are satisfied that these bones came from the pit, though obtained from workmen. These workmen offer for sale various objects from the gravel and Gault, and in no case has any attempt been made to dispose of objects clearly brought from elsewhere.
Since writing the above we have found among the bones deposited in the Sedgwick Museum fragments of antler collected from this pit in 1888, which are recorded on Mr. Gray’s authority as Cervus tarandus.
No worked flints of any importance have yet been found. A flake with platform and bulb may have been derived. In any case it gives no clue as to age, and we may make the same remark about half a dozen spalls (flakes) with bulbs which have been picked up.
The occurrence of the base of the Pleistocene deposits of this pit at a depth of about 6 feet below the surface of the alluvium of the Cam which abuts against them is a fact of considerable importance. As the base of the gravel further south is some feet above the surface of the alluvium and is falling northwards, the existence of a deeper buried channel below the alluvium is probable, and receives support from a section figured by Professor Hughes in the paper cited (fig. 26) and from the accompanying account of the deposits. He: states that ‘‘ the Jesus College gravel with mammoth runs to a depth of some 30 feet below the lower end of Maid’s Causeway” to which the alluvium extends. These Jesus College gravels occur under similar conditions to those at Barnwell Station, which is only a mile distant down the river. They are therefore probably of the same age, and it is certain that in each of these two sections we have Pleistocene deposits below the level of the surface of the modern alluvium. The actual centre of the channel may well lie further under the alluvium, and extend to a greater depth below its surface than the 30 feet recorded in the case of the Jesus College gravel. The situation of our plant-bearing deposits therefore recalls that of the Arctic Plant Bed of the Lea Valley described by Mr. 8. Hazzledine Warren (Quart. Journ. Geol. Soc., vol. lxviii, p. 218, 1912, and vol. Ixxi, for 1915, published 1916, p. 164. .
In the case of the Lea Valley deposits, the lowest terrace in which
R. W. Shufeldt—Exztinct Bird from South Carolina. 343
the plant-beds occur appears, according to Mr. Warren’s account, to be cut through by the buried channel, whereas the evidence at Barnwell is in favour of the view that the beds belong to the deposits filling a channel of that nature. Whether that be so or not, the significant feature is the similarity of the floras of the two districts. Mr. Reid permits us to state that in the case of the Barnwell beds ‘the assemblage is essentially that of the Lea Valley”’.
The occurrence of this flora in' low-level gravels in the Lea and Cam Valleys encourages us to hope that it will be discovered else- where, and it is very desirable that the lowest Pleistocene gravels of other river-valleys should be examined for similar deposits.
Ill.—New Extinct Brrp From Sourm Caronina. By R. W. SHUFELDT. (PLATE XV.)
ARLY in January, 1916, Dr. O. P. Hay, of Washington, D.C., referred to me for description the fossil bone of a large bird that
had been discovered in the eastern part of South Carolina some time previously. This specimen I at once recognized as the lower extremity of the right femur of some bird belonging to a species much larger than any existing form in the United States. I find this specimen to be thoroughly fossilized and of a dull-black colour, the edges of both condyles being considerably chipped off. On the antero-internal aspect the shaft appears to be cut away as if by some shaving implement. This, and where the shaft is broken nearly squarely across above, - exposes a filling of a dense, very hard, pale-grey matrix, with a grain as fine as clay. Judging from this there should be no doubt but that this femur was a thoroughly pneumatic one in the living bird, and that the thickness of the osseous wall of the shaft was by no means great, as may be appreciated by examining the figures on the accompanying Plate XV. ~ Upon measuring, I find the extreme length of this specimen to be 75 millimetres, and its greatest transverse width below (intercondylar), 40 millimetres. Antero-posteriorly, the external condyle measures 25 millimetres (the inner lip of the fibular cleft), and the corresponding diameter of the inner condyle is about the same. No especial effects of pressure or distortion from the same mark this fragment, which is, in every particular, quite typically ornithic in character. Superiorly, the shaft is nearly cylindrical; but, immediately below the point of fracture, begins to expand and to become, antero-posteriorly, flattened and much broadened, until it terminates in its condylar enlargements. In front, the intercondylar or ‘‘rotular channel’’ does not extend up the shaft beyond the condylar ridges, while posteriorly the popliteal area exhibits but little concavity, the whole being much in the same plane. There is, however, an independent excavation immediately above the internal condyle upon this aspect of the bone.
The external condyle is subcircular in outline upon its outer aspect, while the usual fibular cleft or notch is deeply unpaged upon its posterior aspect (Fig. 4).
344 Rh. W. Shufeldt—Eatinct Bird from South Carolina.
Passing to the internal condyle, we find that it too is, upon lateral aspect, subcircular in outline, its postero-superior termination being produced upwards in a more or less prominent way, behind the above described independent excavation (Fig. 1). The intercondylar valley averages about 7°5mm. in width, being concave from side to side, and convex in the opposite direction. This fragment weighs 23 0z., and has been marked with a red capital letter S on its anterior aspect immediately above the intercondylar valley. From this I am assured by Dr. Charles Schuchert, Curator of the Geological Department of the Peabody Museum of Yale University, © in his letter to me of February 25, 1916, that the specimen belongs to the ‘‘Scanlon Collection, and it has been loaned to Dg Jalen
As to the formation from which this specimen came, I would say that Dr. Hay believed it to be Miocene, and this was also the opinion of Dr. Vaughan, of the U.S. Geological Survey, who likewise kindly examined it for me in February, 1916. It presents the general appearance of fossil bones of vertebrates from that horizon, and the question seems to be definitely settled by Dr. Earle Sloan, of Charleston, South Carolina, who says in his letter to Dr. Hay of February 29, 1916, in reference to these phosphatic fossils from the Stono River, South Carolina, near its source, whence the present specimen came, that ‘‘ Nearly all of the vertebrate fossils (many of the cetacea and squalidae excepted) are junior in origin to the phosphate bed, the cavernous interstices of which they entered with their associate supernatant ooze (described as Salkehatchie Ooze), which purely from stratigraphic relations I regard as of late Miocene - origin.
“Tn this connection I beg leave to refer you to my Mineral Catalogue, pages 330 to 336. Also to page 472, which relates to the phosphatic ooze designated the Salkehatchie Ooze.
‘‘'The Scanlon fossil collection was in the main taken from the rock dredged from the bed of the Stono River nearits source, or about - fifteen miles from the present coast line of the Atlantic, but coinci- dent with the old shore line of the Middle Miocene.
‘The Mastodon teeth presented by me to the Museum were dredged from the bed of the Coosaw River, which represents the former wide estuarine area of several minor streams, most of which was sub- sequently covered by the Salkehatchie Ooze and subsequent sediments, marshes, etc.
‘The Mio-Pliocene beds enclose many reworked rounded fragments of the senior phosphate bed, but have nowhere been observed under- lying Salkehatchie Ooze; therefore it is my opinion that the greater portion of the vertebrate remains in contact with the Old Miocene phosphate beds are late Miocene.”
On February 6, 1916, at the U.S. National Museum, I compared this fragment of ‘the lower end of the right femur with the corre- sponding part of that bone belonging to birds of many groups existing in North America, and also with a number in my own collection of avian skeletons, as well as with certain fossil femora figured by me in my ‘ Review of the F ossil Fauna of the Desert Region of Oregon,
R. W. Shufeldt—Eaxtinct Bird from South Carolina. 345
with a description of additional material collected there”.' In that work I figure, on pl. xxxvi, fig. 431, the left femur of Olor paloregonus, Cope, natural size, anterior aspect, which is as big as an anserine fowl when it existed, but was very little more than half the size of the bird the femur of which I am now describing.’ For example, I compared this fossil with the right femur of the Secretary Bird of Africa, with Pandion, with several eagles, with Vultur monarchus, and with various owls of large size, but very marked characters distinguished it from the lower end of the femora of any of these birds. In other words, this fossil femur did not belong to any genus, near or remote, of the Striges, nor to a diurnal representative of the Raptores. For similar reasons it could not be classed among the Cathartide, as a careful comparison with the femur of the Condor of South America and with the corresponding bone of the California Vulture (Gymnogyps californianus) showed very distinctive differences. Both the Condors and the Secretary Bird possess a marked excavation in the popliteal space above the condyles; while in Vultur the external lip of the fibular notch is, superiorly, drawn out into a somewhat conspicuous little process. This process is very well developed in several, if not in all, of the North American eagles.
‘Somewhat similar differential characters demonstrated the fact that this fossil femur never belonged to any bird at all related to Sula, or. to any of the herons, or to Pelecanus, all of which have femora possessed of some characters, which, though not of wide difference, are quite sufficient to constitute discriminating ones, and to point to the fact that this great extinct fowl did not belong in any of those groups, as we now know them, osteologically.
This fossil end of a femur possesses no marked characters that point to any relationship with any large gallinaceous bird—still less to any struthious form, as an ostrich or the like. With negative results, I also compared it with the femur of various species of the Phalocro- coracide, the Pheenicopteride, and the Colymbide and their congeners.
alt belonged to a big bird, having no especial affinities with any of these, certainly not with any of the great toothed loons of the Cretaceous.*
Passing to the Anseres and to certain of their allies, near and remote, it at once appeared that certain characters in the specimen under consideration presented very evident points of agreement. In a specimen of Olor buceinator (No. 18509) at the National Museum, the femur appears to be non-pneumatic. Thisisaskeleton I prepared myself many years ago in New Mexico, where I had no facilities for thorough cleaning, and it is just possible that the femur may be, to some extent, pneumatic. There is a skeleton of Branta canadensis in the same collection that appears to be to a degree pneumatic. This would, apparently, be contrary to certain previous statements
1 American Museum of Natural History Bulletin, vol. xxxii, art. vi, pp. 123-78, New York, July 9, 1913; see pl. xxxvi, fig. 431. - 2 BE. D. Cope, Bull. U.S. Geol. and Geogr. Surv. Terr., iv, pp. 387-9, 1878. 3 0. C. Marsh, Odontornithes, pl. xiii, figs. 1-4.
346 BR. W. Shufeldt—Extinct Bird from South Carolina.
of mine in some particulars, but not in all; in any event it would not invalidate the evident resemblance and certain actual agreements of this fossil specimen with the thigh-bone of several anserine genera and others remotely related to them.*
In Chauna torquata the femur is very pneumatic, and this bird has long been suspected of having certain relationships with the Anseres, as have the Palamedeiformes generally.2, The general facies of the femur of Chauna bear not a little resemblance to the specimen in hand, though in the first-named bird the rotular channel is relatively deeper. The external condyles in the two are very similar. This likewise applies to Olor and to other swans, but to Branta and other genera of geese to a somewhat lesser degree.
In other words, as far as this fossil fragment of a femur will carry us, I am of the opinion that it belonged to the skeleton of some very large, generalized, anserine bird, which existed, during late Miocene times, in the eastern section of this country and probably elsewhere. As faras the fragment carries, it confirms the affinity of the Screamers (Palamedeiformes) with the Anseres, but it throws no light upae the anserine affinities of the Flamingoes.
Inasmuch as we have already discovered the fossil remains in this country of such ponderous swan and goose species as Anser condont, Shuf., and Olor paloregonus (Cope), it “should not surprise us to find even bigger ones than these; in my opinion we have one here. Others of large size represent the extinct Gastornithiformes in other parts of the world.®
Confining ourselves to America—although it is doubtless also true of the extinct avifauns of all countries—I may say here that when we find fossil birds in a formation as early as late Miocene, and they are of comparatively large size, it is just possible—indeed, quite probable—that, in the case of.some of them, they may represent an ancestral type, from which has descended several branches to be represented in the existing avifauna. Upon the extinction of the early ancestral stock, it is often very puzzling to conjecture what the true relations of the forms, genera, and families in existence may be that were derived from the aforesaid ancestor or ancestors. It is: not at all unlikely that the fossil here described may be the ancestral type of several groups still in existence in this country or in the Americas. In this connexion it would be well to bear in mind the possible relationships of the Anseres, the Palamedeiformes, the Phcenicopteride, and others.
Finally, the fossil I have here described appears to be not unlike
1R. W. Shufeldt, ‘‘Osteology of Birds’?: New York State Hducation Department, State Museum Bull. 130, 1909, pp. 330-40. Attention is especially invited to what I say on p. 335 as to the femur in Branta agreeing with that bone in Olor. There are, of course, certain minor swan and goose characters of this bone, which can be both recognized and appreciated, and which would properly fall in the category of ‘* general and special characters ”” otherwise; the statement there made will hold good. »
2 BR. W. Shufeldt, ‘‘ An Arrangement of the Families and Higher Groups of
Birds’’: Amer. Nat., vol. xxxviii, Nos. 455-6, pp. 833- Bi Nov. —Dec., 1904.
> R. W. Shufeldt, ibid., p. 337.
GuHou. Maa., 1916. PoatE XY.
DISTAL PART OF RIGHT FEMUR OF EXTINCT BIRD FROM SOUTH CAROLINA.
Palaochenbides mioceanus, gen. et sp. nov.
cee Pe
R. W. Shufeldt—Eatynct Bird from South Carolina. 347
the one I figure in another connexion, that is, fig. 74 of pl. lv of my paper, ‘‘ Further Studies of Fossil Birds, with Descriptions of New and Extinct Species”: Amer. Mus. Nat. Hist. Bull., N.Y., vol. xxxii, art. xvi, p. 290, August 4, 1913.1 The bone there figured is of a left femur, while the one described in the present article is from the rzght pelvic limb; and in so far as I am able to judge from the cited fig. 74 the two bones are wonderfully alike, both in the matter of form and proportions. Unfortunately, the femur shown in fig. 74
- is so firmly fixed in its flinty matrix that the popliteal area cannot
be examined properly. To all appearances, however, the femoral condyles were of the same size and form; and had I had these two specimens together at the time the bone in fig. 74 was described, it is quite possible that, by the aid of the greater number of exposed characters in the specimen described in the present article, I would have referred them both to the same species, or at least to the same
genus. In fact, the Miocene types of both the gallinaceous birds and the anserine ones may have had not a few osteological characters
in common. For this extinct and probably largest anserine bird discovered in America up to the present time, I here propose the name of Palao-
chenoides mioceanus,* gen. et sp. nov.
In preparing this account I am indebted to Dr. O. P. Hay for various courtesies extended to me during the time the material was in my possession; to Dr. Earle Sloan, of Charleston, S.C., for
information with respect to the discovery of the specimen and the
formation to which it belongs; and to Mr. J. H. Riley, of the Division
-of Birds of the U.S. National Museum, for assistance in selecting bird
skeletons in the collection of that institution for comparison with the material in hand.
EXPLANATION CF PLATE XV.
Fie. 1.—Direct outer aspect of the distal part of the right femur of Pal@o- cheniides mioceanus (extinct). All the figures are natural size, and are reproductions of photographs of the specimen made by the author.
,, 2.—The same bone on direct inner side view. Here the specimen is slightly tipped toward the observer in order to show the matrix filling the thin, hollow shaft. This tipping causes Fig. 2 to be somewhat shorter than the other figures.
,, 3.—The same specimen viewed directly from in front.
AUNT i be oe behind.
1 IT am not responsible for the title given pl. lvii of that paper; and on the page cited I say that it appears to have been a gallinaceous fowl, but that the material does not admit of a scientific reference.
2 Generic name = Gr. maAaids = ancient, + x7v, a goose, + oedys, having a resemblance to, or, in other words, having the general characters of, some of the very early ancestors of the anserine birds. Sp.=Gr. welwy = less, + Kaivds, recent: a subdivision of the Tertiary named by Lyell.
348 Dr. Du Riche Preller—Crystalline Rocks, N. Piémont.
ITV.—Tue Crysratitine Rock-arEeas oF THE PI£MONTESE ALPS. II. Norrarrn Prémont.
By C. 8. Du RICHE PRELLER, M.A., Ph.D., M.I.E.E., F.G.S., F.R.S.E. (Concluded from the July Number, p. 313.)
Ill. Tue Lanzo, Ivrea, anp Vat Susta Area. (Figs. 1! and 4.)
\HIS, perhaps the most complex crystalline area of the Piémontese Alps, is also eminently su? generis, for it forms a unit of rocks outside, and different from the great cale-schist horizon with pietre verdi of secondary composition. As previously stated, itis the continuation of the mica-schist and minute gneiss belt which skirts the Po Valley from the Rocciacorba group to Avigliana, Monte Musiné, and Lanzo, and, extending from Lanzo to Ivrea, Biella, and Val Sesia, reaches beyond the latter into Lombardy to Lakes Orta and Maggiore. Within the Piémontese Alps, viz. from Lanzo to Val Sesia, it is bounded on the north by the calc-schist and pietre verdi fringe which skirts the Monte Rosa gneiss massif, and on the south by the Pliocene and Pleistocene deposits of the Po Valley, its superficial area being roughly 90 by 15 kilometres or 1,350 square kilometres, equal to over 500 square miles. The lower hills of the southern margin vary from 600 to 900 metres in altitude, which in the centre of the area increases to 1,000 and at the northern margin to 2,500 metres. In its general direction south-west to north-east, the area is intersected more or less at right angles by the following affluents of the Po: Stura di Lanzo, Malone, Orco, Chiusella—Dora Baltea, Elvo—Cervo, and Sessera—Sesia. The valley floors vary at the lower limit of the crystalline area from 300 to 500, and in their upper parts from 600 to 1,000 metres in altitude.
As distinguished from the crystalline schist and pietre verdi zone of the Maritime, Cottian, and Grajan Alps, Gastaldi labelled the Lanzo—Val Sesia area the ‘‘ external crystalline zone’”’.? Gerlach,*as early as 1869, designated it as the Ivrea dioritic zone, from the conspicuous outcrops of diorite within and outside the great morainic amphitheatre of the Dora Baltea Valley around Ivrea, which town is itself built on diorite.4 Within recent years it has come to be called the dioritic-kinzigitic zone, chiefly in consequence of Franchi’s and Novarese’s surveys,° and in order to give due prominence to the
[The text-illustration (Sketch-map) given in the previous part (p. 306) is largely referred to here in the second part of this paper.—ED. GEOL. MAG. |
* Gastaldi, ‘‘ Studi geol. Alpi Occid.’?: Boll. R. Com. geol., 1871, p. 3 et seq.
* Gerlach, Die Pennischen Alpen, 1869.
* The lakelets S. Michele, Campagna, Sirio, Pistone, and Nero immediately north of Ivrea, near Montalto, within the moraine wall of Serra d’Andrate, all lie in the diorite zone.
5 C. F. Parona, ‘‘ Valsesia e Lago d’Orta’’: Atti Ist. Lomb., vol. xxix, -
Milano, 1886. V. Novarese, ‘‘ Trattato Weinschenk Zona d’Ivrea’’: Boll. R. Com. geol., 1905, p. 181 et seq.; ‘‘ Zona d’Ivrea’’: Boll. Soc. geol. ital., 1906, p. 176 et seq. 8S. Franchi, ‘‘ Zona dioritica-kinzigitica Ivrea-Verbano”’ : Boll. R. Com. geol., 1906, p. 270 et seq.; ‘‘ Anfibolo secondario del grupp
glaucofane in una diorite di Val Sesia’’: ibid., 1904, p. 242.
- ; H Fig. 3. Sketch Plan of Lanzo Valleys, Grajan Alps. |
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Fig. 4. Sequence of ‘ ‘3 Crystalline Rocks in Biella Cervo Valley, Northern 460. Piémont.
Fig 3. S=serpentine: A=amphibolites, prasinites and euphodites ; P=peridotite and |herzolite ; CS =calc-schist ; “MS = mica-schist.
350 Dr. Du Riche Preller—Crystalline Rocks, N. Piémont.
eclogitic gneiss formation in the Sesia Valley and east of the same, which has its equivalent in the Kinzig Valley of the Black Forest, where it was first recognized and so named by Fischer as early as 1868. Another equivalent formation is that of the hilly area near Monteleone, bordering on the Mediterranean in Calabria.! In all the three cases, the rock, greenish brown in colour, gneissic in aspect and structure, but more fine-grained, micaceous, and less quartzose than primitive gneiss, is often granitoid, and, besides triclinic felspar and quartz, contains garnet, omphacite, biotite, sillimanite, and graphite as associated minerals.
From Lanzo to Val Sesia, the sedimentary crystalline formation concomitant with the Sesia gneiss is that of eclogitic mica-schists, viz. with garnet, omphacite, and blue glaucophane, corresponding to those of the Aosta Valley. With the mica-schists and occasional minute gneiss intercalations are associated dark-greenish, sericitic, calcareous, and quartziferous Permian schists. Both are overlain here and there by isolated masses or patches of Lower Triassic, more or less crystalline and dark dolomitic limestone, the remnants of a much more extensive formation removed by denudation. In the mica-schist formation are intercalated—
(1) he continuous belt of biotitic and amphibolic diorite which covers 50 by 5 to 10 kilometres in length and width, and is flanked on its southern margin by granite, and on its northern margin by minor belts of peridotite, serpentine, and biotitic and pyroxenic porphyrite.
(2) Isolated masses of gabbro, peridotite and lherzolite, granite, syenite, and porphyry.
The coarse-grained gabbro and the peridotitic masses together with those of granite and syenite, associated with minute gneiss and mica- schist, are prevalent more especially in the hills between Lanzo and Ivrea, where a number of interesting, mostly quarried exposures occur at Balangero, Corio, Levone, Rivara, Cuorgné, Belmonte, Locana, Vidracco, Castellamonte, Baldiserro, Muriaglio, Lessolo, and Traversella, in and between the Malone, Oreo, and Chiusella Valleys at levels from 400 to 800 metres altitude. Extensive masses of granite and syenite also crop out north of Biella in the Cervo Valley, while east of Biella to Val Nesia and Lake Orta runs, parallel to the diorite belt, a continuous belt of grey and reddish granite 2 to4 kilo- metres in width, flanked on the south by a large lenticular mass of red porphyry which extends to Borgosesia in the lower Sesia Valley and thence to Lake Maggiore.
1 R. Ugolini, ‘‘ Kinzigite di Monteleone, Calabria’’: Atti Soc. toscana Pisa, 1911, p. 55 et seq.
2 'The eclogitic mica-schist formation with pietre verdi has revealed a con- siderable variety of jadeitic and jadeitoid rocks which S. Franchi, V. Novarese, and A. Stella discovered both in nodules and blocks in situ and as pebbles in the alluyia of rivers in various parts of the Piémontese Alps. -These eclogitic and chlorito-melanitic rocks correspond with the Neolithic implements of Piémont, thus proving the latter to be, not exotic, but indigenous. ‘‘ Nuovi Giacimenti roccie giadetiche ’’: Boll. R. Com. geol., 1900, p. 119; Boll. Soc. geol. ital., 1903, pp. 130, 135, 141.
Dr. Dw Riche Preller—Crystalline Rocks, N. Piémont. 351
The great diorite belt begins near Castellamonte (408 m.) in the Orco Valley, about midway between Ivrea and Lanzo, crosses the Dora Baltea at Ivrea (267 m.), Montalto and Bio, continues north-east to Donato, Ceresito, Graglia, Pollone, and Biella (410 m.), traverses the Cervo, Valley at Andorno (600m.), and thence extends to Val Sesia between Varallo (450 m.), Scopa, and Scopello (650 m.). From Donato, close to the great eastern moraine wall or Serra d’Andrate, the diorite is flanked on the left by serpentine and porphyrite belts, each about 1 kilometre in width, which extend for about 20 kilometres to the Sessera Valley, midway between the Cervo and Sesia Valleys.
In all these isolated and continuous masses of basic and acid eruptive rocks the structure is prevalently massive and granitoid, rarely schistose, with essentially primitive elements without alteration by metamorphism. Peridotite and lherzolite are much more in evidence than the altered product serpentine. The granite with white and pink felspar, very little mica, but rich in quartz, is made up of smaller elements than ordinary, granite. Both it and the syenite masses of Traversella and Biella are closely related to the diorite which at Pollone, near Biella, becomes micaceous, then quartzose, and then passes into granite. The greenish-grey granitoid diorite with hornblende and biotite, often garnetiferous, is essentially massive and unaltered; only in contact with peridotite or gabbro is there an occasional tendency to prasinitic alteration by decomposition, but without contact metamorphism. The dioritic and porphyrite belts, although running parallel for 20 kilometres, are nowhere in direct contact, but always separated by a band of serpentine, mica- schist, or sericitic, quartziferous schist. The porphyrite (Gastaldi’s melaphyre) contains occasionally, e.g. near the Oropa Sanctuary above Biella, lenticular blocks of mica-schist, the former thus having probably consolidated somewhat later than the latter. The sericitic, quartziferous schist is of the same greywacke type as that flanking the diorite belt of Gran Nomenon and of Val Cogne in the Aosta Valley. Between those two diorite belts, linked by the intermediate diorite mass of Locana in the Orco Valley, there is, as already mentioned, obviously a zonal connexion. The locality of Locana is also remarkable for its considerable outcrop of greyish-green lherzolite—a bank 300 metres in depth—which rock Baretti! found to be composed of 75 per cent of olivine, and 25 per cent of greyish- yellow enstatite and green diopside.
As previously mentioned, the Ivrea diorite belt reaches north-east to the upper Sesia Valley above Varallo, where it becomes schistose and gives place to the so-called Sesia gneiss which, further east, in the Strona Valley north-west of Lake Orta, takes the name of Strona gneiss. Both gneisses are of the kinzigitic type already described, ihe Sesia variety being rich, the Strona “variety poor in mica. The apparently abrupt cut-off of the diorite in Val Sesia was formerly regarded as evidence of a great hiatus due to a fracture fault; in reality, however, the diorite has its sequel between the Sermenza and Mastellone Valleys north and north-west of Varallo, where the
1 M. Baretti, ‘‘ Studi Gruppo Gran Paradiso’’?: Mem. Acc. Lincei, Torino, 1876, p. 195 et seq.
352 Dr. Dw Riche Preller—Crystalline Rocks, N. Piémont.
kinzigitic gneiss is largely developed in its schistose form, associated with gneissiform, schistose diorite, norite, gabbro, and peridotite. The gneissic sedimentary rocks, known as stronalites,' are frequently intercalated in the eruptive series and vice versa. This high-level complex, reaching up to 2,500 metres altitude and including the schists of Fobello and Rimella, constitutes Gerlach’s second, separate, upper dioritic zone; but, as Franchi and Novarese” have shown, it forms an integral part of the entire Lanzo—Ivrea-Verbano (Lake Maggiore) dioritic-kinzigitic area. A branch of the kinzigitic gneissic schist extends from the upper Sesia Valley west by Val Vagno and Croce Rossa into the, upper Gressoney Valley, and thence connects with the eclogitic mica-schist of Val Pellina. In Val Sesia the mica-schist extends from Varallo down the valley, and is succeeded by the transverse granite belt, and then by the great porphyry mass of Borgosesia already mentioned.’ It is a noteworthy feature that the Lanzo—Lvrea—Sesia zone descends to the very edge of the Po Plain, whereas along the western ridge of Lake Maggiore and beyond the kindred rocks are only found at high levels, the general direction of dip being thus north-east to south-west. Stratigraphically the whole Ivrea—Val Sesia area within, the Piémontese Alps presents the important phenomenon that all the eruptive masses are infolded in the mica-schist and gneiss formation conformably with the latter without any evidence of angular intrusion. This close association and relationship points to the entire crystalline, viz. both the sedimentary and the eruptive, series being of the same age, that is, Permo-Carboniferous. Lithologically, it is noteworthy that while the eruptive series includes every conceivable combination of felspar, quartz, and mica as primitive elements, the only rock conspicuous by its absence is diabase, probably because it associates more readily with the more highly magnesian calc-schist than with the mica-schist and gneiss formation. It is, of course, quite impossible within the limits of this paper to describe in detail the outcrops in the numerous localities between the terminal points of Lanzo and Val Sesia. Suffice it therefore to state that from Lanzo to Ivrea and Biella the general vertical sequence is, in ascending order, mica-schists and eruptive rocks overlain by subordinate and isolated masses of indubitably Lower Trias crystalline limestone, while from Biella to Val Sesia the sequence is essentially one of juxta- instead of superposition. Of this superficial sequence the most typical example is the section, about 12 kilometres in length, along the Cervo Valley from Montesinaro to Andorno above Biella, which is shown in Fig. 4, and includes the whole eruptive series of old parallel lava streams infolded in the mica-schist
1 The rocks of the Val Sesia and Val Strona region are described in detail in E. Artini and G. Melzi’s ‘‘ Ricerche petrogr. e geol. Val Sesia’’: Memorie R. Ist. Lomb., xviii, p. 219 et seq., Milano, 1900. '
2 Op. cit., 1905, 1906.
3 There is apparently no passage from the granite to the porphyry or vice versa, but Franchi found (op. cit., 1906) a vein of porphyry in the granite mass, pointing to a somewhat later stage of eruption of the former within the same geological period. 4
Dr. Dw Riche Preller—Crystalline Rocks, N. Prémont. 358 formation. It was first pointed out by Gastaldi as early as 1871,' and cutting, as it does, right across the crystalline area, is still the most extensive and instructive, as it is also the most easily accessible section of the whole region.
IV. Conctiustrons.
The description given in this and the preceding papers of the six principal crystalline rock-areas of the Piémontese Alps, condensed and summarized though it necessarily is, will, I think, convey an
‘ adequate idea of the eminently characteristic geological and petro- logical features of each group. Though unique in their collective variety they reveal a certain uniformity of phenomena which from my own observations leads to the following conclusions :-—
1. The pietre verdi, primitive and secondary, appear at all levels from the valley floors of 400 to the highest points 4,000 metres in altitude. Except the prevalence of pietre verdi with primitive elements in the minute gneiss and mica-schist, and of those with secondary elements in the calc-schist formation, there is no order of succession, superposition, or distribution.
2. The basic pietre verdi of all the areas, as well as the acid rocks of the Ivrea belt, are of eruptive origin, but not generally intrusive in the cale-schist and mica-schist formations. They appear in the latter not as irruptive, or as angular injections with apophyses, but as intercalated, lenticular, alternating, and concordantly stratiform planes and masses which sometimes produce the effect of pseudo- intrusive phenomena. There are frequent passages between the eruptive rocks, and from them to the sedimentary rocks and vice versa; but there is no reliable or conclusive evidence of contact ‘metamorphism.
3. The close association of rocks of different origin is in the first instance the result of repeated compenetration of eruptive viscid masses and of sedimentary deposits in course of consolidation. After ‘the resultant formation of conformable, alternating, interstratified planes as a submarine process of long duration, the rocks thus associated passed through the second phase of being raised and folded simultaneously during repeated earth-movements. The eruptive rocks of the Piémontese Alps are therefore of the same age as the infolding cale-schist and mica-schist formations respectively.
4. The process of pressure-heat- and hydro-metamorphism of both the sedimentary and eruptive rocks, already in progress before their emergence, continued not only during the repeated periods of raising and folding, but during the repeated Pliocene and Pleistocene glaciations under the long-continued, superincumbent, and shearing pressure of the ice, and the hydrating, decomposing action of perco- lating water, together with infiltrations from the Pliocene sea of the Po Valley. ‘The dissolving action of the water thus imprisoned and circulating was intensified by the high temperature which it took from the rocks, in conjunction with thermal, highly magnesian springs at various depths.
1 Gastaldi, ‘‘ Studi geol. Alpi Occid.’’: Boll. R. Com. geol., 1871, p. 3 et seq., p. 17.
DECADE VI.—VOL. III.—NO. VIII. 23
354 Dr. Dw Riche Preller—Crystalline Rocks, N. Piémont.
5. The formation of different groups and combinations of basic and acid rocks out of the submarine, viscid, heterogeneous magma slowly welling up from the reservoirs of molten material in the centres of eruption, took place according to chemical and mineralogical affinities, the basic material separating out, grouping, and crystallizing more rapidly, the acid more slowly. Hence the basic rocks of the Ivrea belt were probably consolidated at a somewhat earlier stage than the acid rocks, but within the same geological period.
6. The transformation of the pietre verdi with primitive to those with secondary elements is the combined result of metamorphism and of decomposition by hydration which led to the modification and re-formation of the decomposed elements to secondary groups and combinations. This process is much less in evidence in the pietre verdi of the older or mica-schist than in those of the younger or calc-schist formation, the mica-schist being much less permeable and magnesian than the cale-schist. The transformation probably took place in many cases during the initial stage of consolidation after the eruption of a highly magnesian magma in the cale-schist formation, e.g. in the areas of Monte Viso and the western part of the Lanzo valleys.
7. Chemical and mineralogical affinities produced in some cases basic rocks which, though frequently associated, preserved their separate entities, e.g. the associated but separate belts—originally parallel lava streams—of diorite and porphyrite (melaphyre) of the Ivrea area; or again, peridotite and gabbro and their derivatives serpentine and euphodite. The frequent veins and dykes of gabbric in peridotitic rocks show that the former compenetrated the latter when these, as the more basic, were already in course of submarine © consolidation or, alteration. Secondary amphibolites and prasinites are derived not only from diorite and diabase, but very largely, by metamorphism, from gabbro and euphodite which, in common with the other pietre verdi, also decompose readily to serpentinous schist or pseudo-serpentine. The gneissiform, calciferous, and schistose pietre verdi are the result, in some cases, of pressure- metamorphism, e.g. gneissic gabbro, gneissic diorite, etc.; in others of compenetration and metamorphism of sedimentary and eruptive material from tuffs and muds, e.g. diabasic and porphyric schists, or in relation to calciferous rocks, amphibolic and pyroxenic ‘‘calcefiri’? and serpentinous ‘‘ ophicalce”’.
8. The principal earth-movements experienced by the Piémontese Alps after their emergence came from the south-east, viz. from the Mediterranean and the Po Valley, as is shown by the precipitous and greatly folded flanks of the Maritime and Eastern Cottian and Grajan Alps which, together with the Lanzo—Ivrea—Val Sesia area, formed a coastal region contiguous to the Po Valley. Another, intermediate movement proceeded from the west and corrugated the great synclinal cale-schist formation. The principal fracture- faults of the Piémontese Alps are: (a) in the south, the transverse faults of the Stura di Cuneo and of the Col di Tenda and Vermenagna Valleys, along the north-western and eastern bases of the Argentera massif; (6) in the north, the transverse fault along _
Dr. Fourtau—Echinid Fawna of the Neogene. 355
the Dora Baltea Valley; and (c) the great longitudinal subsidence zone south to north along the eastern margin of the Maira—Dora massif contiguous to the Po Valley. ‘his subsidence or flexure zone, bordering on the Pliocene sea, probably extended along the base of the Lanzo—Iyrea—Val Sesia area and thence to the region of the lakes, thus constituting the zonal flexure or settling zone consequent upon the raising of the Alps in Hocene—Miocene times.!
Such is, in my view, the consecutive operation of causes and effects which produced the phenomenal masses and groups of eruptive rocks, their intimate association with the crystalline sedimentary formations, and the alignment and configuration of the Piémontese Alps of the present day. In their infinite variety they offer both geologically and petrologically an inexhaustible field of fruitful and fascinating study, and more especially does this apply to the pietre verdi, which Gastaldi rightly described as the great ‘‘ magnesian zone”, and whose elusive complexity ever reveals new problems without apparent finality.’
V.—On ree Ecurnip Fauna or THE Nrocenrt Formations.
By R. FourtTAU, Member of the Egyptian Institute.
HAVE just finished the revision of the Neogene Kchinids of Egypt preserved in the collections of the Cairo Geological Museum. Before the publication of this work, which will form the fourth fascicule of the Catalogue of the Fossil Invertebrates of Egypt, it has seemed to me that it might be useful to consider the fauna as a whole, drawing from it some conclusions as to the paleobiology y of the Neogene seas of Egypt. I wish further to ascertain i the Echinids of this region can be of some aid as regards the stratigraphical divisions, and in synchronizing these with the divisions already established in the other regions of the ‘Neogene basin of the Mediterranean.
The materials which I had before me for study were, in the main, collected by the late Mr. Barron in the Miocene region situated between Cairo and the Isthmus of Suez, and also in South-West Sinai. Those obtained by Dr. W. F. Hume in the Gebel Zeit area and by Dr. John Ball at Gebel Tanka, and in the neighbourhood of the mining region of Um Bogma (Sinai), have supplied valuable information, to which must be added interesting specimens collected by Mr. H. T. Ferrar at Mogara (Libyan Desert), by Mr. Hillman from the neighbourhood of Siwa Oasis, by Mr. J. Couyat-Barthoux in the Isthmus of Suez area, by A. E. Pachundaki and by myself in the neighbourhood of Mersa Matru on the Mediterranean coast of Egypt, 185 miles west of Alexandria. I have been able to identify
1 Vide my previous paper, ‘‘ The Moraine Walls and Lake Basins of Northern Tialy,,”” GEOL. MAG., September, 1915, p. 409.
“ The peculiar liability of the whole Italian peninsula to geological changes _ by eruptive and seismitic phenomena, past and present, was aptly emphasized by Professor A. Issel, of Genoa, the present President of the Geological Survey Department. Asked when the geological map of Italy, begun fifty years ago, would be finished, he replied: ‘‘ like Penelope’s web, never.’’
356 Dr. Fowrtaw—Echinid Fuuna of the Neogene.
in these materials eighty-two definite forms (species, mutations, or varieties referable to twenty-three different genera).
The Holostomata are not numerous; Cvdaris avenionensis, Desm., is represented by somewhat numerous radioles and some isolated plates; Leiocidaris scille, Wright, by tests and segments. The ‘‘oangue’? of one of these tests contains some radioles which are very different from those attributed by Lambert to this form — (J. Lambert, Heh. mioc. Sardaigne, p. 18, pl. i, figs. 11, 12). On the other hand, at a higher horizon than that of Z. sev/la, radioles are present similar to those figured by Lambert, and which I have named ZL. geneffensis. The ZL. sismondai, Mayer, is represented by a unique specimen from the point of view of its preservation, an entire test in no way deformed by compression having been obtained by Dr. Hume in the Inner Zeit Valley, also by fragments of tests of some size and fairly numerous radioles.
The Glyphostomata belong for the most part to the Echinine. The Psammechinus are numerous, eight different forms, some of which give evidence of indisputable passages to the sub-genera Anapesus, Holmes, and Schizechinus, Pomel; thus showing the little value to be attached to these determinations, of which the utility never seemed clearly demonstrated. In close relations to the Psammechinus are a number of small sea-urchins, to which certain authors, who ascribe an exaggerated importance to the very difficult study of the pedicellariz, which themselves are not found in the fossil state, have wished to place in the T'emnopleuride, although they have neither true or false pits nor low sutural impressions, and their plates are not united by dowelling. These sea-urchins, attributed formerly to the genus Arbacina, Pomel, of which the type A. monzlis, Desm., has sutural impressions which are sometimes very difficult to observe, have lately been separated from it by Lambert et Thierry and been placed in the genus Prionechinus, Al. Agassiz. Unfortunately, this genus Przon- echinus has been wrongly defined and, moreover, imperfectly figured by its author, so that one is led to inquire if the fossil forms quite agree with the characters contemplated by Agassiz when he established this genus. Consequently I am of opinion that a new determination is necessary, and have proposed for this Echinid the name Pseudo- arbacina.
I have also pointed out that among the Zemnechinus of the Gaj Series of India, the 7”. stellulatus, Duncan & Sladen, may be separated from this genus because it does not possess the false pits or low sutural depressions which characterize Zemnechinus, Forbes, Ope- chinus, Desor, and true Arbacina, Pomel. As 7. stellulatus presents a peculiar ornamentation, having its secondary tubercles united with the primary ones by radiating miliaries, it must be considered as the type of a new genus of the Triplechinine, for which I propose the name Brochopleurus. A form allied to B. stellulatus has been found by A. E. Pachundaki in the Miocene range of the Marmarica near Mersa Matru, and described in 1907 by Lambert under the name Opechinus fourtaut.
The Temnopleuride are only represented in Egypt by a new form belonging to the genus Lepidopleurus, Duncan & Sladen.
Dr, fourtau—LEchinid Fawna of the Neogene. 357
The Gnathostomata are represented by forms belonging to the genera Echinocyamus, auct. (non Lambert), Scutella, Agassiz, Amphiope, Desor, and Clypeaster, Lamarck. Two forms, one Miocene, £. stellu- latus, Capeder, the other Pliocene, Z. puszllus, Miller, represent the first genus. The Scutelle are represented by six forms all peculiar to Egypt, the Amphiope by three species, of which one, 4. palpebrata, Pomel, is characteristic of the Burdigalian of Portugal and Algeria. Finally, the genus Clypeaster is represented by one Pliocene species and by eighteen from the Miocene. It is interesting to note that all the Miocene forms in Egypt are low or of very small elevation, and nowhere in this stage have those grand types of notable dimensions been met with so frequent in the Neogene of the Western Mediterranean, not only in Algeria, but also in Spain, France, Corsica, Sardinia, in Upper Italy, and more rarely in Malta. The presence in Egypt of depressed forms such as C. intermedius, Desmoulins, C. marginatus, Lamarck, and C. martini, Desm., or of moderately high ones such as C. crassus, Agassiz, C. scille, Desm.., and OC. subdecagonus, Peron & Gauthier, forms which are found in the western regions, forbids the hypothesis of difficulty or discontinuity of communication between the oriental and occidental basins of the Miocene Mediterranean, and the more so that with the Pliocene there appears in Egypt a representative of the group of C. altus, Klein, the C. egyptiacus, Wright, which is so polymorphic that certain of its specimens display the typical aspect of the ancestral form and of its variety, the C. portentosus, Michelin. We are therefore led to think that this absence of forms, with thick and very high tests in the Egyptian Miocene, is due to the composition of the waters and the littoral deposits of this sea, which did not contain sufficient carbonate of lime of the calcite type so assimilable as to permit the Clypeaster developing the plates of their test in sufficient thickness and the pillars of their endoskeleton destined to support the inflation of their
_ambulacral rosette.
The Atelostomata are as abundantly represented as the Gnathio- stomata, and by a larger number of genera.
The Pliolampas, Pomel, are represented by three forms, of which one, P. welschi, Pomel, is known in Algeria. chinolampas, Gray, has twelve species, of which three, Z. plagiosomus, Agassiz, EH. monte- sinensis, Mazzetti, and £. pignatarii, Airaghi, belong to the Cono- clypeiform group; the others are all true Echinolampas with test of small elevation. One only, Z. hoffmanni, Desor, is Pliocene.
The genus Pericosmus, Agassiz, is only represented by the typical species, P. latus, Agassiz, which is very abundant at several levels. The genus Brissopsis, Agassiz, is also only represented by a particular race of B. crescenticus, Wright, B. fraasi, Fuchs. There is only one representative of Agassizia, A. zitteli, Fuchs. The genus Opisaster, Pomel, is represented by two forms which appear to be successive mutations of the same type, O. lovisatoi, Cotteau, and O. almerat, Lambert. The specimens of Schizaster, Agassiz, are in general so badly preserved that it is only possible to mention two species with certainty, S. eurynotus, Agassiz, and 8S. legraini, Gauthier. The genus Zrachyspatangus, Pomel, is represented by 7. tuberculatus,
358 Dr. Fourtaw—Echinid Fawna of the Neogene.
Wright, which is also found at Malta, in Corsica, and in Sardinia. The existence of Spatangus corsicus, Desor, in Egypt, is not definitely established, but S. pustulosus, Wright, can be mentioned without hesitation.
Maretia (sensu lato), Gray, is represented by two forms peculiar to Egypt, I. fuchst, Oppenheim, which appears to be a simple mutation of M. tuberosa, Fraas, which, in its turn, might in’ reality only be a variety or race of ‘lu. ocellata, Defrance. I have not thought it necessary to maintain the genus Memipatagus, Desor, the primary tubercles of the Egyptian forms have deeper ‘‘scrobicule”’ than those of the present-day Maretia. These ‘‘ scrobicule”’ in reality only produce swellings in the interior of the test and not the ‘Campulle’”’ so characteristic of the genus Lovenia, Desor. If the M. ocellata from the Miocene of the neighbourhood of Bordeaux have, as says Lambert, scrobicular “‘ ampulle”’ in the interior of the test, the question will arise whether they should be separated from the genus JMaretia, and also if they agree with Defrance’s type, which came from the Rhone basin, and with the Swiss neotype, the only one figured to this day by Agassiz and de Loriol, who never made any reference to the presence of these ‘‘ampulle”’ in the specimens they studied.
Two Miocene forms of Zoventa are new and peculiar to Egypt. Finally, the genus Lchinocardium, Gray, is represented by three species; two of these are Miocene, of which one is £. depressum, Agassiz, and the third is of Pliocene age.
As regards geographical distribution, we have been able to note 35 forms common to Egypt and the western basin of the Mediterranean, including 9 Miocene Clypeaster. Of these forms 12 are present in Algeria, 21 are found in the Miocene of Italy and the Italian islands of the Tyrrhenian Sea, 8 exist in Malta, and 14 in the Neogene of the Rhone basin in France, and up to the present 40 apes to be special to Egypt.
It is interesting to lay special stress on the presence in Egypt of a representative of the genus Lepedopleurus, which till now has been exclusively Indian, and of a form very near Brochopleurus stellulatus, Duncan & Sladen, also from India.
From the paleobiological point of view (leaving aside the Pincers Echinids, which have only been found in Egypt in a single locality near the pyramids of Giza) a quasi-independence can be noted between the two Egyptian Miocene basins to the east and west of the Nile Valley respectively, which only have five forms in common and three species, represented by varieties in each basin. Of species with Indian affinities, one is in the eastern basin and the other in the western. It should be noted that the Lower Miocene is represented in these two basins by two forms common to both: Scutella zittelv, Beyrich, and Schizaster legraint, Gauthier.
We may explain this dissimilarity of fauna by the difference of the facies in the two basins. In fact, the Middle Miocene deposits of the western basin are nearly exclusively formed by a mass of very ferruginous and siliceous hard limestones, interbedded with more or less sandy layers and overlying a detrital formation of ferruginous
Dr. Fowrtau—LEchimid Fauna of the Neogene. 359 sandstones. Only flat Clypeasters are found in these beds. In the northern part of the eastern basin, between Cairo and Suez, the Lithothamnium and foraminiferal beds alternate with soft sandy limestones and coral reefs. Their fauna is richer and the Clypeasters are higher, whilst the southern part of the same basin possesses a very sparse fauna, this being due, in spite of the abundance of limestones, to the influence of the phenomena which have given rise to the oilfields.
On the other hand, the Lower Miocene deposits are detrital or of purely littoral origin in the western basin, whilst in the eastern basin their facies indicates neritic and bathyal formations except at the eastern foot of the Geneifa range, where they are littoral as in the western basin.
Now, the abundance of Scutelle, which in places form a very shell-breccia, indicates a general facies of littoral or sub- littoral characters, this being confir med by the relative rarity of the Cidaride *- and also of Brissopsis, an essentially deep-sea genus.
STAGES. HORIZONS. CHARACTERISTIC HCHINIDS. Upper Plaisancian— | Clypeaster egyptiacus, Wright. Neogene. Astian. Echinolampas hoffmanni, Desor. Western Basin. EKastern Basin. 4 ( ’ Middle Vindobonian. | Amphiope fuchsi, Four- | Leiocidaris sismondat, Neogene. tau, Scwtella huntert,| Mayer, Clypeaster isth- Fourtau, Clypeaster| muicus, Fuchs, Scutella martini, var. rohlfst, | deflersi, Gauthier, Plio- Fuchs, Hchimolampas | lampas pioti, Gauthier, amplus, Fuchs, H.| Echinolampas amplus, plagiosomus, Agassiz, | var.meridionalis, Four- ‘ H. hemisphericus,| tau. Lamarck. Lower Burdigalian.’ | Scwtellazitteli, Beyrich.| Scutella zitteli, Beyrich, Neogene. Clypeaster depereti, Gauthier, Hchinolam: pas orlebari, Gauthier, Brissopsis crescenticus, race fraast, Fuchs, Maretia tuberosa, Fraas.
From the point of view of stratigraphical divisions and their
synchronization with the horizons noted in the different regions of
1 The recent discovery of the Echinolampas discus, Desor, by Lieut.-Colonel W. EH. Jennings-Bramly, at Gebel Hamamia, near Birket Mogara, in the Western Desert, seems to indicate the presence in Egypt of marine deposits belonging to the lowest horizon of the Neogene, the Aquitanian.
360 A. R. Horwood—Upper Trias, Leicestershire..
the Neogene Mediterranean basin, we find ourselves in the presence of great difficulties, arising from the extreme variation in the character of the fauna and of the lithological composition of the littoral deposits. We have, therefore, to content ourselves by adopting in very broad lines the divisions of Lower, Middle, and Upper Neogene, corresponding to the three Mediterranean stages of Suess, or accepting the terms Burdigalian, Vindobonian, and Plaisancian of French authors, attention, however, ‘being Galled to the fact that the last term includes the Plaisancian and Astian of the older authors. This being established, we can give the following species as characteristic fossils of each of these divisions i in Egypt.
I am indebted to Dr. W. F. Hume, F.G.S., Director of the Geological Survey of Egypt, for ay translating this paper into English.
VI.—Tue Upper Trias or LEICESTERSHIRE. By A. R. Horwoop.? (Continued from May, 1918, p. 215.) (WITH A MAP AND PLATES.) Part II (continued).
Physiography.
Tectonics and River Development. Petrography and Lithology. Paleontology.
Economics and Water Supply. Sections and Correlations. Bibliography.
Appendix.
Pe
4, PHyYSIOGRAPHY.
STUDY of the local stratigraphy, tectonics, petrography, and paleontology leads to some conclusions as to the physiography of the epoch in this district. Even studied as a detached area it may be noticed that the Bunter or pebble deposits are west of the sandstones and marls. From the fact that the eastern limits of the first two are west of the marls, and the second (sandstones) west of the pebbles, and from the evidence of other areas, it appears that this purely local west to east succession is applicable to the whole British area, and itis well known that each member thins from north-west to south-east (as a whole), This is the sequence typical of aqueous deposits, and particularly of delta deposits, and at the same time indicates (in part) the direction from which the sediment came.
Remarks have already been made as to the eastern limits of the Bunter and the Lower Keuper. Borings under later Mesozoic and Neozoic rocks (chiefly in search of coal)* show that the limit of the Red Marl is decidedly further east than that of the Bunter or Lower
1 Aided by a grant from the Government Grant Committee of the Royal Society.
2 See Harrison, Ussher, MeKenny Hughes, and Royal Coal Commission Reports, ete.
A. Kk. Horwood—Upper Trias, Leicestershire. 361
Keuper. It is clear that these facts are intimately interwoven with the three prime movements, Caledonian, Charnian, and Pennine, affecting this area, with the noticeable overlap, erosion of pre-Triassic Jand-surfaces, as well as the causes already mentioned, of the normal deltaic succession.
The sandstone horizons intercalated between the marls, in both Lower and Upper Keuper, when not lenticular, suggest shore conditions, a fact proved by the character of the flora and fauna as well. Usually they retain traces of delta-bedding, which must be taken to mark fluviatile or estuarine conditions: It is possible that some of the lenticular bands may be due to the alternation of seasons of overflow or flood and drier conditions, and represent the sand or silt caught upon normally submerged banks of muddier sediment’ The explanation that these white or grey sandy calcareous zones owe their colour to bleaching, or exposure to atmosphere (and they alone contain ripples and salt pseudomorphs), is corroborative of this suggestion. As they occur in the Upper Keuper in the red beds in what I regard as the lake phase of the delta epoch they would hardly be sediment deposited on river banks as in the Mississippi, but rather accretions to submerged mud-banks, and the difference in the character of the sediment! would be due to abnormal sequence of deposition at flood-times, i.e. thin beds of silt or sand in place of mud over deposits in deeper water, instead of in thick beds near the shore. The alternating sandstones and marls in the Lower Keuper may be in part due to overflow of banks, in part to deposition nearer shore, before the lake phase commenced.
The height to which Red Marl reaches at Bardon Hill is somewhat difficult to explain except upon the supposition that there was considerable oscillation of level, and as in a river valley deposits may be formed at different levels so that the sequence may be obscured, so the isolated marls at Bardon may be regarded as homologous with beds at different levels elsewhere. The existence of Rhetic and Lias outlers west of Charnwood at Needwood Forest and elsewhere indicates that originally Charnwood was not, as now, a lofty peak, but buried in deposits now cleared away by denudation between Jurassic and Glacial times. The relative position of the Bardon Marls, however, in the sequence affords a datum-line upon which to estimate the thickness and extent of strata removed.
The stratigraphic details given show that, as Dr. Matley finds in the Warwickshire area, there is, apart from the south-easterly dip and the radial dip around Charnwood and similar ranges of hills, a marked uniformity in the horizontal character of the beds. This must be discounted in so far as the occurrence of flexures can be indicated in this area by gentle undulations connected with the main movements affecting the Midlands.
A feature to be remarked upon, further, as to the relation of sandstones and marls is the preponderance of the latter in regard to
vertical height and horizontal extent. The proportion of sandstone
* Grey beds more arenaceous and calcareous, of higher specific gravity than the red beds. Carried further out by the increased velocity of the current.
362 <A. R. Horwood—Upper Trias, Leicestershire.
is greater in the Lower Keuper than in the Red Marls. On the whole there is, where the sandstones are fully developed, one-third sandstone to two-thirds marl. In the Red Marl the proportion, even including skerries and thin sandy beds, is hardly more than one-twelfth. This relative proportion of marls to sandstones is, taken in conjunction with their place in the full sequence, following pebble beds, the natural succession in aqueous deposits, especially those originated by a river and forming in due course a delta. :
Not less clear, as seen by a study of the petrography, is the fact that, commencing with the Bunter, the deposits graduate upwards into finer and finer sediments right up to the Rheetics. It is true that there are interbedded coarser sands in the marls high up, but these are explained as abnormal in the lake phase, and they are as a whole most predominant between the pebble beds and the lower part of the Upper Red Marls, their proper position in a delta succession.
In the Coal-measures laid down under delta conditions, there are rock courses or ancient river-beds in the lower part of the Middle Coal-measures. They do not appear higher up, and it is clear that the highest red beds, like the Red Marls, represented the lake phase. In the Trias we should not expect to find traces of the river-bed higher than the Lower Keuper, and though there is no strict analogy to be pointed out, yet in Bunter and Lower Keuper delta bedding and wedge-bedding and similar obscure types of deposition indicate that a river-bed might be sought if sections existed under Liverpool or in that direction, assuming one river came from the north-west. —
The direction from which the sediments came may be to some extent proved by the occurrence of extraneous material for which a definite source can be adduced. Thus the occurrence of galena in Carboniferous Limestone nodules in the Lower Keuper at Shepshed, which is found in situ at Dimmingsdale to the north-west, furnishes one indication. Coal has been found also in the Upper Keuper Sandstone at Leicester, and it is reasonable to assume that this also was derived from the north-west, or the Ashby Coalfield. ©
The constant occurrence of current or delta bedding, noted in many instances in describing the stratigraphy, both in the Lower Keuper Sandstones and the Upper Keuper Sandstones, shows that, on the whole, they follow the direction of dip to the south-east (from north- west). When beds are uniformly bedded in this way it is usually held that, as in the Coal-measurtes, river agency produced the oblique laminations. This, again, points to the direction of the river and source of sediment.
Again, the evidence of ripples shows that the period was marked by constant shallow-water conditions, and the presence of land in the vicinity, with intervals of depression between. ‘The ripples trend largely north-west and south-east in the Red Marl, varying mostly in the Lower Keuper, to the opposite direction, and in the latter the dip is also more variable. I consider the crest of the ripple was parallel to the direction of the flow, and do not think they were produced by a river at right angles from the south-west, but were formed by lateral ebb and flow. It has been suggested that in the variegated
A. Rk. Horwood—Upper Trias, Levcestershire. 363
beds the grey bands are bleached out by drainage along the lines of more porous beds, since they were covered up. But this cannot be so, because they differ in chemical composition and specific gravity from the Red Marls, and they alone contain ripple-markings. As to the absence of ripples in the red beds, this is natural because they are thicker, laid down in water originally deeper where ripples could not be made, while in the shallow sandy grey beds (nearer land or super- ~ posed in flood-time on submerged mud-banks) they are general.
An analogy for the grey beds overlying red beds is found in the Magdalen Islands, in the Gulf of St. Lawrence, where there are purple sandstones with a persistent covering of white sands, decoloured by organic acids. A recurrence of this each time would explain the repetition of variegated beds.
Suncracks occur commonly on the surfaces of the Lower Keuper marly beds, and in a few cases in the flaggy beds in the Upper Keuper Sandstones, testifying to the periodicity of terrestrial surfaces and the proximity of land. The association of footprints with them proves that the phase was of some duration. Rainprints occur with the suncracks, especially in the Lower Keuper in North and South Leicestershire, indicating that (as they are numerous and abundant) the climate was not particularly arid, since large amphibious creatures lived along with plants such as Equisetacew which required excessive moisture. A somewhat modified type of climate existed similar to that met with in the Coal-measures suitable for the formation of thin carbonaceous layers (incipient coal-seams), and if the occurrence of bitumen can be attributed to a similar origin (unless it is volcanic, for that also may be suggested), though it was undoubtedly drier and
' less humid, and the sun-rays were not obscured, as it has been
doubtfully suggested they were in the Coal-measure period. The widespread occurrence of pseudomorphs of salt crystals in Lower and Upper Keuper suggests that shallow water lay for periods
’ upon flats that were allowed to evaporate before they were submerged
again. The preponderance of brine thus indicated, as well as by the occurrence of brine in Triassic waters, bears out the old view of the saline character of the waters, and justifies the old name ‘‘Saliferous Red Marls”. That salt occurs in abundance in dry regions with similar pseudomorphs is well known. We need, however, to take into account the innumerable other indications that the period was one in which water was the prime agent of importance.
Besides the continuous thick gypsum bed, not far below the Tea- green Marls, there are a number of other horizons at which it occurs A the Red Marl, as shown by the Crown Hill and other borings. It is also found in the Lower Keuper, but here as in the Orton Sandstone Group the bands are thinner. As a rule they are continuous, and a marked feature is their horizontality. This and the thickness of the band near the top make it clear that the gypsum was deposited in shallow lagoons liable to be inundated. Its frequent association with Green Marl and Skerry suggests it was formed at seasons of flood followed by drier periods allowing desiccation. It is probable that the reticulated bands and some ball | ‘gypsum are of secondary origin, formed by infiltration from above. The nodules at
364 | A. R. Horwood—Upper Trias, Leicestershire.
the Star Brick Pit show a stage in which carbonate of lime was more plentiful than sulphate of hme. The occurrence of brine (see Water Supply) in some abundance in Triassic waters, evidenced also by the salt crystals, shows, as does the presence of lime combined as sulphate and carbonate and as pure lime, that marine conditions were not far removed from the lacustrine phase, or else that from the land side a different source was being tapped totally unlike the highly aluminous Red Marl or lacustrine phase. That Rhetic beds were being laid down further east during the Red Marl period here would account for such marine incursions. If water with brine and coarse sediments were swept westward temporarily they would naturally give a different result under abnormal conditions from the deposits in the typical Rheetic sea.
The occurrence of beds of bitumen in the Lower Keuper Sanaa is an indication that either carbonaceous deposits were laid down as in the Coal-measures, or else that it was poured out by volcanic agency as a subsidiary lava-flow. But it is not usually held that coal is bituminous in this sense, so that the second view must be held. It has even been suggested that gypsum may have owed its origin to a similar agency, voleanic activity, the water causing the sulphur emitted to be precipitated as a sulphate of lime. Volcanic activity is known in the Permian to have been extensive, but to what extent, if any, in Keuper times is uncertain.
The coloration of the rocks at present is a matter of difficulty. If the green colour was original or the red colour conveyed in chalybeate waters,’ the investment of each grain must have been by a movement. from below upwards to explain intervening green bands, unless these were bleached as each grey horizon was at the surface, as may be suggested, and it may then be said that the red intervals indicate the amount of submergence after each such bleaching.? Intimately connected with it is the difference of physical characteristics, composition, and specific gravity of the red and green bands (see Petrology). Variegation was due to two processes. Firstly, the grey bands were decoloured after being coloured red by organic acids. at the surface, being formed in shallow water over mud-banks and exposed to the air, where worms, possibly bacteria, etc., may also have played a part. This denotes oscillatory movements. Secondly, the sandstones heavier and containing more calcareous. matter may have been laid down at flood seasons as the grey bands probably were, but in this they were perhaps never submerged again after they were raised along the higher levels of the river-head. Being derived from a different source they differ in constituents. from the marls.
The desert conditions described in connexion with Mountsorrel Croft, etc., all relate to granitic or syenitic rocks. Frost and heat, alternating with cold, help to disintegrate granite, and it is lable to split up into blocks. The sand thus formed accumulates as a talus. Even a slight wind will set up sand-blast action, causing polished surfaces. As we examine the eastern boundary of the
1 Accepting Dr. Moody’s view. * Following deposition of red colour.
A. Rk. Horwood—Upper Trias, Leicestershire. 365
Trias not far from the delta-head, it would be natural to find at this point a considerable extent of blown sand and dunes at the bar of the delta. But the evidence is confined, in the Soar Valley, more or less to a level of 300 feet O.D.
The sort of conditions prevailing then, locally, show that in Lower Keuper times the sediment which was detrital, laid down under estuarine conditions, thickened westward, and the waterstones and marls became transitional to the next phase (lacustrine). In the Red Marl phase calcareous strata thickened eastward, arenaceous westward, as in the Coal-measures according to a general law, but on the whole the sediments thin to the south-east, and were laid down under lake conditions, the river being gradually absorbed. Some agency contributed to the unsuitable state of the waters for organic life (sulphurous?), but at rare intervals some submerged land arose and animal and plant life were able to subsist for a time. Probably in this way the flora and fauna were markedly migratory.
During the Rhetic phase in England (earlier on the Continent) initial marine conditions arose, and the Keuper waters gradually lost their distasteful character, though the stunted fauna at this time shows that there was a struggle for existence. The Triassic flora and fauna, as a whole, do not bear any resemblance to those of dry regions to-day, but rather resemble in composition those of the estuaries, swamps, and lagoons in and around the mouths of large rivers and their banks, which, again, have a direct communication with the sea.
The Upper Carboniferous was a period during which the surface was depressed, with periodic elevations. During the Permian there. was depression for lacustrine and marine conditions, and elevation for the manifestation of volcanic activity. The Trias at its commence- ment was an elevated area, and there was a gradual submergence or subsidence up to Rhetic times with intervening oscillations and periodic elevation. The conditions may be summed up in tabular . form thus :—
Bunter. River. Torrential or pluvial| N.W. Scotland, in fluviatile. Midlands, Lickey’s : Hartshill, etc. (quartzites, etc.). Lower Keuper. River. Formation of head | Millstone Grit, Coal- of delta and lagoons | measures, Permian. (estuarine).
Upper Keuper. | River, merging | Lacustrine (waters | Granites and syenites into lake, with | sulphurous). of Midlands, Coal- overflow of silt. measures, Sand-
stones, etc.
Tea-creen Marl. ne a Estuarine and lacus-
trine initially ma- Ditto. ; : rine.
Rheetic. Transition from | Initial marine phase. | Ditto, Coal-measures,
lake to sea. shales for . detrital matter, carbonate of lime from organisms.
366 <A. R. Horwood—Upper Trias, Leicestershire,
5. Trcronics anp River DrveLopmeEnt.
Any consideration of tectonic structure must be, to some extent, affected by the evidence of denudation preceding and following the formation, of which the structure is discussed.
There is considerable local evidence of pre-Triassic denudation in post-Carboniferous and pre-Permian times. ‘This is shown by the absence of higher beds in the Ashby district. It is shown also by the occurrence of hematite nodules in Permian beds containing plants derived from the Coal-measures. There is evidence in the Permian that locally the deposits are non-sequential, due either to land-oscillation or denudation. The Lower Keuper, as has been intimated, is locally deposited on the eroded surface of the Bunter, a feature noticed also in the Newark district. The character of the Triassic sediments indicates that the Palseozoic rocks were greatly worn down to furnish the source of their material.
The evidence of the Drift deposits shows that much of the Trias has been denuded by glacial agency, the extent of which cannot be estimated. Furthermore, the probable formation of an earlier pene- plain between Liassic and recent times and a later one giving rise to present drainage systems must account for much modification in the configuration of Central England. The loss of the Keuper between Mesozoic and Pleistocene times was probably considerable, evidence of which is afforded by marls low down at 880 feet at Bardon, and the existence of outliers of Rhetic beds at Needwood Forest, west of the Charnian range. ;
The general structure of the Upper Trias may be summed up as
‘follows: The Lower Keuper is characterized by the sloping nature of the scarps formed by the sandstone features. A series of stone beds near the top forms a small escarpment below the Orton Sand- stone Series, as in the east of the Mease Valley and south of the River T'rent. The marly beds form flat country as in the Mease Valley, and less so north and south of the Trent.
The lower part of the Red Marls present gentle slopes up to the escarpments of the sandstones of the Orton Group in the Mease Valley, and between Castle Donington and Kegworth, exhibiting sinuous flexures. ‘he sandstones form ridges, a medified plateau on plateau structure along the top of the escarpment, and where they broaden out and are exposed at the surface they afford flat tablelands. ‘The marls below exhibit gentle dip slopes.
The Upper Keuper Sandstones, Dane Hill Series, occur as high eround witha steeper, less marked dip slope, and as the sandstone beds are more massive, but local, the hills present only small plateaux.
In Notts the Red Marl is characterized by steep slopes with sharply defined upper margins bordering the flat plateaux, which descend gradually to the south-east, representing the dip slope of the marls. Here, though the position of certain skerries can be ascertained, their extent as in Leicestershire cannot be followed, and in this district the Drift obseures wide tracts: The skerries give rise to flat plateaux, and on the gentle dip slopes form sandy belts. ‘This character is noticeable also in Leicestershire. In the Melton district, in the absence of features formed by skerries,
A. R. Horwood—Upper Trias, Leicestershire. 367
the country is gently undulating with occasional conspicuous hills, crowned by patches of sandy drift. Over a great part.of Leicester- shire this feature is well-marked.
There is no doubt that the alternation of hard skerries or sandstones and soft marls causes to a great extent (along with drift mantles) this type of country with ridge and furrow on a large scale. ‘The occurrence of these undulations are evident from Gloucestershire as far as Newark.
The same sort of differentiation may be attributed to the Lower - Keuper, and the position of stone beds at the top of the waterstones about Appleby up to Normanton, as in the Notts district noticed by William Smith, is of a similar order. The same features occur around Kegworth. Flat-topped hills are formed by the sandstones in the Notts district.
In general the dip is south-east as a whole, but varies from point to point in direction and degree, a fact which must be put down to the existence of undulations that can only be indicated provisionally. Another cause for variation in this is the necessarily radial or quaqua- versal dip around Charnwood Forest, and submerged granitic and syenitic knolls. Away from these last, where it exceeds the average amount of 1° to the south-east and differs in direction (as noted earlier in this paper under stratigraphic details, and vide Map), it may be concluded that there are a series of synclines and anticlines with dome structure, as observed in Gloucestershire by Mr. Richardson and in Warwickshire by Dr. Matley. As remarked, the Lower Keuper exhibits in Leicestershire most variation, because its outcrop is less obscured by drift than the Red Marl, where few dip calculations can be made (except radial dip around Charnwood, etc.). And it has been noted already that in places the waterstones thicken locally to the west. In Notts they thicken westward at Burton Joyce, Thurgarton, and Newark, due to an actual thickening or to a persistence of sandy beds higher up in the Marl Series, or to both causes, as noted by | Mr. Lamplugh.
It is plain that the earth-movements preceding the Triassic period have affected the later rocks, and that folds then produced have influenced beds of later age, the folds being accentuated by subsequent movements. The Pennine Chain, which was initiated after the Coal- measure period and before the Permian, is one of these, running north and south. It is probable that it has acted upon the later Triassic rocks in the Kegworth district.
Disturbances in the Lias near Barrow show the influence of move- ments north-east and south-west, or Caledonian in character. Faults such as the Sileby and Barrow fault are of Charnian type, north-west and south-east in trend. All these three movements have not only influenced rocks earlier or later than the Trias, but these earlier faults have also been affected by the later ones.
The strike is mainly north-east and south-west, as in other areas, and Caledonian in direction. The faults at Glen Parva and Spinney Hills, north-west by south-east, are of Charnian character, a direction initiated in pre-Cambrian times, and doubtless this movement has been continuous since. The dome structures of Langcliffe and Enderby
(868 0A. R. Horwood—Upper Trias, Leicestershire.
are of the same type, and have modified the stratification in each case. Some old gullies as at Bardon, also Charnian in direction, are filled with Trias.
The flexures of the Orton Sandstone group suggest that undulations in that direction are due to those of Charnian type. ‘hose at Kegworth may be Caledonian and Pennine, whilst the folds that affect the Upper Keuper Sandstone Dane Hill group are also Caledonian.
Faults are uncommon. A few occur in the Burton district in the Red Marl. ‘Che Lower Keuper is faulted in the Ashby district and at Castle Donington. The Rhetics exhibit faults at Glen Parva, Hast Leake, Spinney Hills, Barkby Thorpe, and at Barrow, chiefly of Charnian direction, or Caledonian. W. Molyneux was the first to suggest the occurrence of flexures in the Red Marl in this district. But he used the term in a different sense. Describing a section at Horninglow, just outside this area, near Burton, and at Tatenhill, he remarked upon the irregular lines of red and blue marl, as having a curved or wave-like appearance. He attributed it there to the unequal distribution of colouring matter in the marls. While the upper sandstone beds are horizontal the lower exhibit curvature, ‘“contortions,’’ or ‘‘ flexures’’. ‘hey are undoubtedly instances of undulations which would give rise to flexures at the outcrop.
Jukes noticed how in the Charnwood district ‘‘ the stratification of the red marl conforms to the uneven surface of the slates, rising up on the slope of its peaks and sinking gently in its hollows, showing its deposition to have been very gradual and tranquil, and also that the slate rocks had been both upheaved and worn into peaks and hollows before the deposition of the red marl”. Writing of the sandstone horizon at White Horse Wood, he says it is ‘‘no doubt the original position in which it was deposited, and not due to its subsequent elevation”; and as to the relation of marls and sand- stones to the older rocks, the two remarkable circumstances are ‘‘their horizontality, compared with the highly inclined position of the beds on which they rest. ‘he second is the height at which they are found, being considerably above that to which the beds of the formation generally attain in the surrounding country”’.
In reference to the denudation of the Trias he says, ‘‘ The original surface of the New Red Sandstone was probably a nearly perfect plane, rising gently on every side towards the Forest, filling its valleys and mantling round its sides, leaving none but the higher peaks exposed to view. Over this nearly horizontal plane lay the Lias, equally, if not more, horizontal, thinning out and ending probably towards the Forest,! but approaching it much more nearly than it does now. To produce the existing undulating surface, all the Lias west of its present irregular and broken boundary, and much of the New Red Sandstone beneath, has been removed by currents of water, [drift] scooping and hollowing it out, and producing the present valley of the Soar and its collateral valleys. Portions of the higher beds of New Red Sandstone, namely the variegated marls, protected by the solid rocks around them, have been left in the Forest to show the
1 At that time the Needwood outlier was not known.
ra
A. R. Horwood—Upper Trias, Levestershire. 369
height the formation once attained,” and to mark the destruction caused by the denuding forces.”
There is no doubt ‘that the influence of the buried landscape of Charnwood Forest has modified the normal bedding of the Red Marl in its immediate vicinity, and the footnote Jukes adds shows that he attributed the radial dip to the true cause, the natural angle of rest of particles deposited on inclined slopes. In exhibiting a resemblance to quaquaversal dip in relation to the surrounding synclines, which meet the deposits showing radial dip, it may be that in some cases. the dip is not always radial in relation to the older rocks, but due to undulations caused otherwise, or as at Enderby and Longcliffe, for instance, to the anticlines of the Charnian range itself.
The height of the Trias at Bardon where skerry bands le high up in the big quarry, whilst capable of more than one interpretation as already remarked, may very probably represent the flexure of a portion of a dome structure of which Bardon is the axis, but the beds cannot certainly be correlated with their continuation at lower levels under the Red Marl, and are only exhibited on one side of the hill. If this interpretation is correct, it does not affect the equal probability that the Red Marl rose on all sides to heights approxi- mating to that reached at Bardon.
Mr. Harrison, in describing the relation of ie Red Marl to the _syenite of Enderby, says ‘‘everywhere they follow the irregular surface of the syenite, in one place filling up a deep hollow in that rock, so as to be perceptibly curved”’. And as to Croft, he remarks, ‘‘Here again we see the Keuper red marls and sandstones resting upon the syenite, from which they slope rapidly away in all directions.”’ It is interesting to note that then,in 1884, Mr. Harrison, in writing of the polished surface of the syenite overlaid by sand and ‘boulders’, remarked that they ‘‘ may have been due to the friction of the sand’’. Thus, while describing this as an ancient sea-cliff (at 320 O.D. like the other horizons) he was the first to suggest eolian agency for this phenomenon locally, as Professor Watts did not describe the wind-polishing at Mount Sorrel till 1889.. The explana- tion of curvatures at Enderby and Croft may be attributed to radial dip influenced by dome structure in the first case, and at Croft initially to radial dip between, more than one submerged peak giving rise to catenary bedding, though it is probable that they are of the same character as the undulations elsewhere.
A. H. Atkins, in noticing ‘glacial markings’? in the Red Marl at Small Heath, near Birmingham, remarked upon the contorted nature of the white bands and of the twisted and broken beds of clay above, and at Adderley Park upon puckerings in grey bands about 6 inches high, like those in Red Marl at Sileby, perhaps. These phenomena were most likely also due to undulations. Hull in 1860 remarked upon the probable influence of an anticlinal in producing the inlier of
1 “Tt is not meant that even the highest beds of the New Red Sandstone ever attained the same general height over the surrounding country which they have in the Forest, as they would naturally be deposited on a gentle slope, rising higher on the sides of the hills than elsewhere.’’ ;
DECADE VI.—VOL. III.—NO. VIII. 24
370 =A. R. Horwood—Upper Trias, Leicestershire.
sandstone at Diseworth, coupled with denudation. He also suggested
the occurrence of a syncline at Smisby of Red Marl.
Under stratigraphy and ante (under Tectonics) I have alluded to the evidence of flexures in the Orton Sandstone group and the Dane Hill group, whereby loop-like outcrops are produced owing to the influence of undulations in the beds themselves. Several circumstances combine to render the data for their delineation on the map frag- mentary, apart from the general obscuring effect of the drift. The Orton-on-the-Hill series is developed along the outcrop, but this is buried to the east under drift and the influence of dip, and cut off to the west by the River Mease, and to the north by denudation of the Coal-measures and higher beds (post-Triassic). Around Kegworth it is buried by drift and cut off by the Rivers Trent and Soar.
The Dane Hill series is actually persistent, but occurs in isolated patches due to (1) Soar Valley excavation, glacial and recent (as well as pre-glacial); (2) covering of drift, and pre-glacial denudation elsewhere. They have been well described by L. Richardson in the Eldersfield district, and by Dr. Matley in Warwickshire. In Notts they have been noticed at Lambley Dumble, and at Barton Joyce by Dr. Sherlock, and influenced by faults at Thorneywood. The dip has been found to amount to as much as 50°. In the Melton area also the dip is thought to be influenced by ‘‘small undulations recognizable in the Lias’’, and between Moorhouse and Barrel Hill Mr. B. Smith noted disturbances following the direction of the dip, and the dip increases in the Gleet Valley, the rocks are gently rolling with the axis of the folds at right angles to the general strike of the beds. In the Ollerton district they have been noted in the water- stones at Rufford Park, and in the Red Marl an anticline trends through Muskham Wood and Eakring, while Goosemoor Dike is excavated along asyncline. Anticlnes occur in the waterstones at Kirton Wood also, in the Red Marl synclines at Mather Wood and Kersall, anticlines and synclines at Bathleyford Bridge, Tuxford. It is thus plain that the undulations in the Trias are of pretty general occurrence. Whilst the flexures produced are largely due, as exposed at the surface, to river development and denudation, their original form was not unlike their present contouring. That these phenomena, when viewed in isolated instances as catenary bedding, cannot be attributed to sagging, is quite obvious when their relation to earlier foldings is recognized. It should also be remembered that apart from these undulations the general dip is south-east, and this was more or less original, whilst the existence of attenuation in some parts to the north-west, along the east outcrop, and in Cheshire, Staffordshire, and Warwickshire accounts for any supposed sagging, attributed to other causes.
The overlapping of the different members is shown in numerous instances, a fact which can only be accounted for by subsidences and deposition by aqueous agency. The Lower Keuper lies in hollows of the Pebble beds, both in the Mease Valley and in Notts, abutting against the ridges they form. The Red Marl overlaps the Lower Keuper, and both the Bunter. The Lower Keuper also overlaps the Permian. It is probable, moreover, that the surface
A. R. Horwood— Upper Trias, Leicestershire. 3871
of the Coal-measures presented an uneven surface for the deposition of different members of the Trias upon it, being also attenuated to the south-east from the north and west, as seen from numerous colliery sections. ‘This overlap is reflected in the discordance between the strike of the different members of the Trias.
Another feature is the gradual passage of the Lower Keuper Sandstones into the Marls, as noted at Austrey and Warton, and of the lateral passage of the sandstones into marls at Heather. This feature is paralleled in the Upper Keuper Sandstone by the thinning of the marls to the west and the sandstones to the east at Leicester, near Hinckley Road, and at Ashleigh House. In such cases we have instances of the occurrence of lenticular bands.
The river development of the Trias depends upon the fact that the main systems of drainage are developed along the line of strike (Caledonian in direction) of the Soar, excavated in the softer beds of the Red Marl. A similar feature is to be noticed in the Mease Valley where the valley forms the junction between the Lower Keuper Sandstones and Red Marls. No doubt the original systems of consequents and subsequents, with the resulting obsequents developed on a more ancient peneplain, is to a large extent modified as regards the Red Marl area in Leicestershire, so far as the present peneplain is concerned by the markedly radial arrangement of streams which are dependent upon the relation of the Red Marl to the old developed surfaces of Charnwood Forest. The developing of this area before the deposition of the Trias caused the system of drainage which largely contributed to the sediments forming the Trias and earlier rocks locally to some extent. The later development of the Red Marls since their deposition and formation of the present contours has been the work of numerous agents of denudation, subaerial in the main, before glacial time, which we have no means of determining. But elacial action itself has paved the way for much of the present system of drainage, causing radial arrangement of streams, together with the agencies that have regulated the present systems of con- sequents and subsequents upon which this radial system is superposed. In this way the river drainage west of the Soar ‘Valley differs from that to the east except whens. as around Billesdon, a similar radial arrangement may also be discerned in beds older than the Trias.
6. PrerrograPHy anD LirHonoey.
As this section affords material for a separate paper, and, owing to reasons into which I need not enter, a bare summary of this even could not be prepared, I have decided to omit this section from the present paper. Reference to ‘‘The British Trias, a Delta System” (Trans. N. Staffs Field Club, vol. xlvii, pp. 100-30) will afford a very brief summary of the character of the sediments examined in this area, together with a comparison between them and the deposits in other parts of the country.
(To be concluded in our next Number.)
372 Notices of Memoirs.
NOTICES OF MEMOTRS.
————-——_
J.—Tse Art or ‘I'repHINING AMONG PREHISTORIC AND PRIMITIVE Proptes. By. T. Witson Parry, M.D., F.G.S. Journ. British Archeological Association, pp. 39, with 11 figs., March, 1916.
R. PARRY has long made a detailed study of the art of trephining the human skull, and now publishes an interesting summary of
the whole subject. Skulls of the Neolithic period undoubtedly trephined during life have been discovered several times in France, but only one example possibly of so old a date has hitherto been met with in Britain. This is reported to have been found with remains of the Irish deer, in peat at Port Talbot, South Wales. Two specimens which certainly belong to the Bronze Age have been examined by Dr. Parry, one from a cist at Mountstuart, in the Isle of Bute, the other from a long barrow near Bisley, Gloucestershire. Two other trephined skulls, one from Hunsbury Camp, near Northampton, and the second from the Thames, near Hammersmith, are probably of later date. These are the only examples of trephining hitherto found in Britain. It may be added that the Hammersmith skull has now been placed in the London Museum, where it is exhibited with an explanatory collection arranged by Dr. Parry.
II.—Recorp or a Prenisrortc Inpusrry In TasuLrar FLint ar Brambripcge AND HieHrierp, NEAR Sovraampron. By R. EH. Nicnoras, F.L.S., F.G.S. pp. 92, pls. xli, text-figs. 8. South- ampton: Toogood & Sons, 1916. |
(WVHIS beautifully illustrated little work by the Hon. Curator of
the Tudor House Museum, Southampton, is a series of notes on a large collection of flints which the author has made at two localities near Southampton. ‘The two sites are described, with explanatory diagrams, and the chief characteristics of each specimen are briefly enumerated. Dr. Robert Munro appends two pages of ‘‘ Explanatory Notes”’, expressing the opinion that the working of the flints dates back to the transition period between the Paleolithic and Neolithic civilizations, which is already known by discoveries of similar flints at Cissbury, in the Oban caves, and in other localities.
III.—Uerer Devonian Fisn Remarys From ELtesMERE LAND, WITH Remarks on Drepanasrrs. By Jouan Kime. Report of the Second Norwegian Arctic Expedition in the Fram, 1898-1902, No. 33 (pp. 72, pls. viii, text-figs. 8), 1915. -
(JYHE fragmentary Upper Devonian fish-remains discovered by
_ the late Per Schei in Goose Fiord, Ellesmere Land, have been exhaustively studied at Christiania by Dr. Johan Kier, who describes them in this well-illustrated report. Only one specimen was obtained from the truly marine beds at the base of the series—a head-shield of a small new species of MMacropetalichthys, named after its discoverer.
Notices of Memorrs. 373
Numerous remains of the ordinary Upper Devonian fishes occur in the typical Old Red at the top of the series in association with fossil plants which have already been described by Professor A. G. Nathorst. Fragments of dermal armour of two new species of Psammosteus exhibit well the microscopical structure, of which fine illustrations are given. Dr. Kier also describes for the first time the microscopical structure of the plates of Drepanaspis, which he shows to be closely similar to that of Psammosteus. He agrees with Bashford Dean that the dorsal and ventral surfaces of Drepanaspis are wrongly identified by Traquair, the one being mistaken for the other. A Coccostean fragment and typical remains of Bothriolepis are described, and several large scales are referred to a new species of Holoptychius. Dendrodont and Rhizodont teeth alsooccur. The illustrative plates, by a photographic process, are especially beautiful.
ITV.—On toe Generic Position oF ‘‘ ASTEROLEPIS ORNATA, VAR. AUSTRALIS”’, McCoy; wira Descrivprion or A New. Variety. By Frepprick Cuapmay, A.L.S. Proc. Roy. Soc. Victoria, n.s., vol. xxvill, pp. 211-15, pls. xx, xxi, 1916.
\ R. CHAPMAN shows that the so-called Asterolepid fish from ivf the Devonian of Gippsland, Victoria, described in 1876 by McCoy, is really a Coccostean. A new specimen from the same locality seems to prove that it belongs to Phlyctenaspis or to a closely related genus. Other specimens represent a new variety in which the ornament is very dense, with smaller and more prominent tubercles.
V.—Norice sur ta Nature vE w’Oreane Hexicorat pu HzLICOPRION. By A. Karpinsxy. Bull. Soc. Ouralienne Sci. Nat. Ekatérinebourg, vol. xxxv, pp. 117-45, pl. i, 1915.
Hernicoprion Onerct, n.sp. By A. Karpinsxy. Bull. Acad. Inip. Sci. Petrograd, pp. 701-8, text-figs. 5, 1916. [In Russian. |
R. KARPINSKY, who first described the remarkable spiral of Elasmobranch teeth, Helicoprion, from the Permo-Carboniferous of Russia in 1899, is still making valuable contributions to our knowledge of this fossil. He now describes new specimens from Krasnoufimsk, one of them not less than 350mm. in diameter. He refers to Hay’s discovery of Hdestus in direct association with the cartilages of the jaw, and concludes that there cannot any longer be doubt as to the true nature of Helicoprion. The inner part of one new spiral seems to have been broken during life, Dr. Karpinsky thinks through shock. The teeth in the new species, H. Clercz, are thicker than usual, and exhibit a slight crimping or plication at the base. They are therefore interesting for comparison with those of the new English species of Hdestus described by Dr. Smith Woodward at the last meeting of the Geological Society of London.’
1 See Reports and Proceedings Geol. Soc., infra, p. 381.
374 Reviews—The Geology of the Lake District.
RHVIEWS-
I.—Tue Gerotocy or tHE Laxe District anD THE ScENERY AS INFLUENCED BY GuoLoercaL Srructorre. By J. KE. Mang, Sce.D., F.R.S. 8vo; pp. xii, 220, with 51 illustrations and coloured seological map in pocket of cover. Cambridge: at the University Press, 1916. 12s. net.
| cae geologist who is already acquainted with the Lake Country,
or who is intending to visit it, will be grateful to Dr. Marr for the present volume. In this he has collected his numerous memoirs and addresses in the form of a connected narrative, and as he has also included the results obtained by previous or contemporaneous workers the book forms a complete epitome of what is known of the geology © and physiographical development of the district.
The work is intended primarily for the student, but by printing in smaller type such details as are of special interest to the trained eeologist the author has attempted to adapt it also to the requirements of the general reader. As a rule scientific books which cater for different classes of readers fail to satisfy either, but we think that the present author has succeeded admirably in his object. This we feel is due in the first place to his really intimate knowledge of the district, and secondly to his ability to place the essential facts in an interesting and attractive form, a gift with which readers of the author’s work on Zhe Scientific Study of Scenery are already - familiar.
The book opens with a brief review of the pioneer work in the district, due honour being accorded to Jonathan Otley, the Father of Lakeland Geology, a charming portrait of whom appears in the frontispiece. After a brief summary of the general structure of the district there follows a description of the Lower Paleozoic rocks and of the structural changes which took place in the area after their deposition. In this chapter we have a detailed consideration of the nature of the folding, faulting, cleavage, and metamorphism which has affected these rocks. Three views are quoted in this connexion— (1) that the Borrowdale rocks are in reality older than the Skiddaw slates and brought into their present position by an overthrust boundary fault; (2) that the apparent succession is the true one and that the fault between the two groups is a thrust plane; (3) that the fault at the base of the Borrowdale Series is not an overthrust but a ‘lay fault’ associated with a thrust plane. The latter is the view advocated by Dr. Harker and the author, who conclude that the movement resulted in folds having a general H.N.E. and W.S.W. direction which were accompanied by horizontal movements producing the lay fault between the Skiddaw Slates and Borrowdale lavas and between the latter and the Coniston Limestone. These are accompanied by normal faulting, but also by horizontal movements along vertical planes or ‘tear faults’ with the pro- duction of ‘shatter belts’. It is of interest to note that the
Reviews—The Geology of the Lake District. 375
presence of these ‘tear faults’ was suspected by Sedgwick as long ago as 1831.
The intrusions of Devonian age in the district, namely those of Shap, Skiddaw, Eskdale and Wastdale, and Carrock Fell, and their metamorphic effects are then considered, and the subsequent erosion of some 30,000 feet of Lower Paleozoic rocks, regarding which the author remarks: ‘‘That this erosion affected the highest Silurian rocks indicates that it took place in Devonian times”; as, however, the oldest marine Carboniferous beds of the south-west of England are shown on p. 115 to be absent from the northern district the period of denudation may have continued into Lower Carboniferous times.
In chapter xiii a brief description of the Upper Paleozoic rocks which surround the Lake District proper leads to a discussion of the post-Carboniferous changes, and is followed by a description of the events which occurred between the time of the formation of the dome in Tertiary times and the Glacial period. ‘his is followed by an account of the Glacial period, and the volume concludes with a short description of the post-Glacial changes in the district. These later chapters, which are chiefly concerned with the development of the present scenery of the district, will probably be among the most interesting to the general reader.
The book is fully illustrated with bleak and white maps and sections in the text reproduced from previous publications by Dr. Harker and the author, including a large-scale map of the Shap Granite and its associated metamorphic rocks, while an admirable coloured geological map on the scale of 4 miles = 1 inch, for which the author acknow- ledges his indebtedness to Dr. H. H. Thomas, is contained in a pocket in the cover. The only criticism we would make in this is that the upper beds of the Ordovician and lowest of the Silurian are represented by the same colour, so that there is no visible division between the .two systems on the map. This was doubtless determined by the technical difficulty of dividing a very varied outcrop, while from a physiographical standpoint the Stockdale Shales and Coniston Lime- stone are closely associated in producing the Yendale Valley and similar depressions to the south of the volcanic massif. The book is further embellished by numerous half-tone photographs in the text, which have been well selected to show the leading features of Lakeland scenery.
This volume, which will henceforth take its place as the recognized authority on this area, is notable not only on account of its admirable detailed summary of what is definitely accepted regarding the geology of the Lake District, but also for the clear indications regarding the points which still require elucidation. With this volume before him the future worker ambitious of forging the remaining links in the chain of evolution of this fascinating region will indeed have cause to bless the name of the gifted author of the Geolog gy of the Lake. District.
376 Reviews—French Tertiary Polyzou.
II.—Conrrisutions To A Strupy oF 'prriary Potyzoa.
1. Conrripurions A L’ETUDE DES Bryozoarrns FossItEs, No. xiv, Bryozoaires DU Stampiren. By F. Canv. Bull. Soc. Géol. France, ser. Iv, vol. xiv, pp. 147-52, pl. iv, 1914.
2. Lxs BryozoaIRES FOSSILES DES TERRAINS DU Sup-OvEST DE LA France, No. vii, Rupéiren pe Gaas. By F. Canv. Bull. Soc. Géol. France, ser. Iv, vol. xiv, pp. 465-74, pls. xiv—xv, 1914.
N these two papers M. Canu continues his investigation of the French Tertiary Polyzoa. Im one he discusses the age of the Argiles de Gaas, and concludes that they are Rupélien (—Stampien), instead of Latdorfien (=Sannoisien) as hitherto considered. The Polyzoa contained in them had already been described by Reuss, and of the seventeen species obtained by M. Canu by washing 15 kilogrammes of the clay, fifteen had already been recorded by the former author. One new species is described and a new genus founded for one of Reuss’ species.
The material of the other contribution was from the Marnes 4 Huitres of Fresnes-les-Ruigis, of Stampien age, and is chiefly remarkable for yielding three recent species, from the occurrence of which M. Canu is led to the conclusion that ‘‘ Les marnes a Huitres de Fresnes-les-Ruigis paraissent s’étre déposées par 20 ou 25 metres d’eau au voisinage d’estuaires de petits cours d’eau”’
III.—Mesozorc anp Crnozorc Maorrina or rae Paciric Coasr oF Nort America. By Eart L. Pacxarp. Univ. California Publ. Bull. Dept. Geol., vol. ix, No. 15, pp. 261-360, pls. xii-xxxv, MOTO.
HIS memoir is based on the study of a large number of fossil and living Mactrine from North American: Pacific Coast regions between Mexico and Alaska, belonging to the Universities of California and Washington. The author adopts the taxonomic system proposed for these molluscs by Dr. W. H. Dall during 1889 and subsequent years, in which was emphasized the importance of the Pelecypod hinge-structure for purposes of classification. In discussing the various elements of the Mactrine shell attention is directed to its general shape, the position of the beaks, the type of the pallial line with its sinus, the muscle-scars, and the dental armature. Form- variation is illustrated by a series of ‘eraphs’ showing ratios of lengths to heights. Contours vary from a trigonal to an elongate type, their many “variations having been observed to exist within the limits of certain species, while ‘others are much more constant. Systematic descriptions are given of the different species represented, under the genera Mactra, “Mulinia, and Spisula, these being divided into a number of sub-genera and sections. Those species recognized as new to science include Spisula brevirostrata and S. mercedensis (Pliocene); Mactra trampasensis, Mulinia pabloensis, and Spisula
Reviews—North American Paleontology. 377
selbyensis (Miocene); Sprsula acutirostrata, S. merriamt, and S. tejonensis (Kocene); and Spisula chicoensis (Cretaceous). A distri- bution table, both geological and geographical, adds to the importance of this work, the species ranging from Cretaceous to recent times. The Miocene is referred to as ‘‘ the period of the greatest generic and specific differentiation of the family’, the older forms being fewer and relatively constant in shape. The author’s able explanations of the taxonomy and phylogeny of this group of shells are rendered still more interesting by the excellent plate-illustrations which adorn the memoir.
R. BLN,
AV.—SrratickaPHy AND Fauna oF THE Tryon Eocene or CaLirornia. By Roy E. Dickerson. Univ. California Publ. Bull. Dept. Geol., vol. ix, No. 17, pp. 363-524, pls. xxxvi—xlvi (chiefly Mollusca and views of localities) and text-illustrations (maps, sections, ete.),. 1916.
‘Y\HE author recognizes four faunal zones in the Tejon Group of
California, which, in ascending order, are named the Zurbinolia zone, the Rimella simplex zone, the Balanophyllia variabilis zone, and the Siphonaha sutterensis zone. Stratigraphical and faunistic details are given of these zones, maps of California being also introduced showing the probable extent of the Tejon sea during the deposition of the rocks containing the different zonal faunas. This Eocene fauna is said to embrace about 300 species, 25 of which range downward into the underlying Martinez Eocene, while 3 or 4 occur in the Oligocene beds above. ‘The species are fully listed from the various localities of the region, while some 15 Pelecypoda and about 30 Gastropoda are described and figured as new species. As geological investigators rarely attempt zonal work on the Tertiary formations, ‘the author deserves our congratulations on his discovery of well- defined zones in this group of rocks, which adds an interest and a greater accuracy to our previous knowledge of these deposits.
Teed a Se
V.—Fauna Srupies 1n THE Cretaceous oF THE Sanra Ana Movn- TAINS OF SourHERN CaLirornia. By Hart Leroy Packarp. Univ. California Publ. Bull. Dept. Geol., vol. ix, No. 12, pp. 187-59, with 1 map, 1916,
lie carrying out his researches on the Cretaceous faunas of the
Santa Ana Mountains, the author recognizes relationships to those characterizing other Cretaceous regions of California, especially with the Chico fauna of Shasta and l'ehama Counties, to that of the underlying Horsetown Series. Foreign affinities of the faunas are more difficult to trace, although it is stated that, according to F. M. Anderson, they favour the Turonian of Europe as well as resembling the life groups as found in the Cretaceous deposits of Southern India.
378 Reviews—North American Paleontology.
The geology of the district includes (1) a basement complex of Triassic - age, (2) the Trabuco conglomerates, which are non-fossiliferous and said to be pre-Chico, (3) Upper Cretaceous (Chico Group), (4) Upper Eocene of Tejon, (5) lowermost Miocene of Vaqueros, (6) Alluvium of Pleistocene age. Three zones are recognized among the Cretaceous rocks of the region, the oldest being the Actaonella oviformis zone, above being the Zurritella pescaderoensis zone, and then the TZellina ooides zone. Full lists of the fossils, which are chiefly of molluscan interest, are given, showing their distribution through the different zones.
TR, 2B NG
VI.—Fauna From tHe Lower Priocenre at JAcatiros. CREEK AND Watrnam Canyon, Fresno Country, Catirornta. By Jorern 0. Nomianp. Uniy. California Publ. Bull. Dept. Geol., vol. ix, No. 14, pp. 199-214, pls. ix—xi, 1916.
HE fauna assigned to this horizon and as listed in the memoir embraces 8 species of Echinodermata, 2 Cirripedia, 49 Pelecy- poda, and 29 Gastropoda, including the description and figuring of the following new species: Gastropoda: Astralium arnoldi, Chryso- domus coalingensis, Iissuridea subelliptica, Durex perangulatus, Natica (Neverita) orbieularis, Trophon magister, Turritella nova; Pelecypoda: Mytilus kewi, Tivela trigonalis. The author points out a close resemblance existing between the Etchegoin and Jacalitos faunas, the former having been recognized as of probably Pliocene age by Professor J. C. Merriam; henee it is considered that the Jacalitos deposits should be regarded as Lower Pliocene, although certain
observers had placed them in the Upper Miocene.
Rie Ne
VII.—Fauna oF THE So-cALLED BoonE CHERT, NEAR BATESVILLE, Arkansas. By Grorcze H. Ginry. Dept. Interior United States Geol. Surv. (George Otis Smith, Director), Bull. 595, pp. 46, PSI ae Oo.
(JVHE rocks with which this memoir deals are of Mississippian age
and therefore belong to the Carboniferous Series. Faunal relationships are traceable between the Boone Chert fossils and those of the Moorefield Shale of Arkansas, but not with the Boone Limestone as has been usually recognized by paleontologists. In a tabulated statement is given the species of the Boone Chert fauna and their occurrence in the Moorefield Shale (chiefly the ‘‘Spring Creek Limestone”’). This fauna consists of Corals, Bryozoa, Brachio- poda (Productella, Productus, Spirifer, Reticularia, etc.), Pelecypoda (Conocardium, Parallelodon), Gastropoda (Bembexia, Huomphalus), Ostracoda (Primitia), and the following new species: Sporifer martinitformis, Martinia (?) pilosa, and Conocardium meekanum var. magnum (= new var.).
Reb ene
)
Reviews—North American Paleontology. 379
VIII.—Faunas or tHe Boonr Lrvesrone at St. Jon, ARKawnsas. Dept. Interior United States Geol. Surv. (George Otis Smith, Director), Bull. 598, pp. 50, pls. i-i1i, 1915.
1: is pointed out in this account that the Boone Limestone includes all the Mississippian rocks of Northern Arkansas and Southern Missouri, comprising equivalents of the Kinderhook, Burlington, and Keokuk formations farther north, while the St. Joe Limestone forms the base of the Boone Series. The Boone Limestone fauna consists of Corals (Amplexus), Bryozoa (Lenestella, etc.), Brachiopoda (Leptena, Productella, Spirifer, Reticularia, Athyris, etc.), Pelecypoda ( Cypri- cardinia), Gastropoda (Platyceras), Cephalopoda ( Celonautilus), Trilobita (Brachymetopus). The following are described as new species: Polypora, n.sp., Hemitrypa, n.sp., Chonetes ornatus, var. arkansanus (= new var.), Productella semicostata, P. patula, P. malle- spinosa, Rhynchopora pingus, Cypricardinia rugosa, Cardiomorpha orbicularis, and Brachymetopus (?) elegans. The fauna of the St. Joe Limestone as observed at St. Joe is also described. It is composed of about forty species, including’ Corals (Zaphrentis, Cyathaxonva, etc.), Echinodermata (Crinoids), Bryozoa (fstulipora, Cystodictya, Henes- tella, etc.), Brachiopoda (Leptena, Chonetes, Productus, Productella, Camarotechia, Shumardiella, Spirifer, etc.), Gastropoda (Platyceras). The author has recognized as new species Fistulipora rubra and Camarophoria simulans. ba Ne
1X.— Borrom Conrrot or MartnE FAUNAS AS ILLUSTRATED BY DREDGING In THE Bay or Funpy. By E. M. Kinpie. American Journ. Sev., vol. xl, pp. 449-61, 1916.
\ ane paper contains some important considerations on the influence
of environment with regard to marine faunas living on sea- -_ bottoms, molluscan life being more particularly alludedto. A number of shells obtained from dredgings in the Bay of Fundy are tabulated, the species having been obtained from differently constituted sea- bottoms which are referred to as: Boulders and Sand, Boulders and Gravel, Black Mud, Sandy Mud, Rocky and Sandy bottom, ete. The author recommends the paleontologist, when using fossils for purposes of correlation, to ‘“‘recognize and bear in mind the close relationship between the physical texture of the bottom and the kind of life living upon it’’.
Ree Ne
X.—Fossiz Contectine. By E. M. Kinpiz. The Ottawa Naturalist, woke xxix, Nos10; pp. 117=24, 1916:
HE author suggests a number of collecting methods when obtaining fossils for study purposes, emphasizing, of course, the importance
of precise localities being attached to each specimen, and the particular bed of the section being noted from which the fossil was procured. The measurement of strata by means of a spirit-level clinometer is also recommended. Remarks are made on paleography, and suggestions offered that complete data should be furnished
380 Reports & Proceedings—The Royal Society.
regarding the physical features of the rocks in which the fossils are found. ‘The essay supplies several more items of information on this subject which should be of interest to paleontologists. ; R. B.N.
XI.—Brier Norticzs.
1. Mexican Grorocy.—The latest batch of Mexican geology was received in London in the middle of July. It consisted of the Boletin and the Parergones del Instituto Geologico de Mexico from 1918 to 1916. Of first importance is the Boletin for 1914, containing G. R. Wieland’s ‘‘ La Flora Liasica de la Mixteca Alta’’, with its atlas (1916) of fifty fine quarto plates. The Parergones to hand includes the whole of vol. vy (1918-16), and is largely occupied with seismological records from 1911 onwards. In part iv (1918) are a variety of analyses of rocks and waters; part v (1913) deals with the water-supply of various Mexican cities; part 1x (1914) is a catalogue of the Mexican rocks preserved at the Institute ; ; and part x (1916) contains more water-supply papers.
2. Inpran Gerotogy.—Mr. C. de P. Cotter has produced a Contents and Index to the Memoirs of the Geological Survey of India, vols. xxi— xxxv (1884-1911), for which the cordial thanks of all geologists are tendered to him.
3. New Guinean Geotoey.—In Reports on the Collections made by the British Ornithologists’ Union Expedition and the Wollaston Expedition in Dutch New Guinea, 1910-13 (2 vols. 4to, 1916 (Francis Edwards), price £10 10s.), vol. 11, Report 20, 1916, Mr. R. B. Newton reviews previous work on the island and then describes the Foraminiferal Tertiary Limestones. These limestones are full of ZLepidocycline, the large forms (ZL. murrayana and LL insule-natalis) and the smal! (Z. swmatrensis), as in the Christmas
Island rocks, and Mr. Newton regards them as indicative of
the later part of the Aquitanian age. An excellent plate of oat micrographic sections by Green accompanies the report.
REPORTS AND PROCHHDIN GS.
I.—TaHe Royat Socrery. June 29, 1916.—Sir J.J. Thomson, O.M., President, in the Chair.
Among other papers read was the following, a summary of which was supplied by the author :—
‘‘New Bennettitean Cones from the British Cretaceous.” By M. C. Stopes, D.Sc. Communicated by Dr. A. Strahan, F.R.S.
The present paper describes two new types of well- preserved fructifications of Bennettites in Britain. One is that of an entirely new species from the Gault; the other is from a Lower Greensand specimen, diagnosed from externals by Carruthers, but not, hitherto described.
4
Reports & Proceedings—Geological Socrety of London. 381
The paper is presented in two parts: (1) the description of the new species; (2) the full description of the vegetative anatomy as well as fructifications of Bennettites maximus, Carruthers. Both specimens are well petrified, yielding excellent microscopic sections.
(1) The ovulate cone of the new species was procured by Mr. G. Walton, of Folkestone, and sent to the author among several other Gault ‘woods’. It appears to have been relatively immense in comparison with other known cones of the group, having a diameter of 70mm. or more, and 600 or more seeds in a single transverse | section. The seeds are five-ribbed, very small (1°2 mm. diameter), fitting into interseminal scales which completely fused to form a hard external ‘shell’ to the complex fruit. The interseminal scales are better preserved than in other species and had a peculiar external ‘plastid’ layer. The various layers of the seed coverings reveal more exact details than are known for other species. Restorations showing the peculiar investing ‘ cupule’ of the seed and also its diagrammatic section are given.
(2) B. maximus, Carruthers, is chiefly interesting as having bisporangiate cones. These are the first such cones discovered in this country, and are interesting in showing ovules at a very early stage in their development, not hitherto described. The peduncle is large, but the fertile part of the cone so small that it is cut in only one section in the series through the cone. The ovules are in an early meristematic state. A restoration is given showing the proportions of the parts and how they differ from more mature cones. The species differ from all other Bennettites in its vegetative anatomy, in having curious pitted ‘transfusion ’ cells in pith, cortex, and leaf- bases, and in the peduncle and bract scales, and in appearing to be
without the ‘gum canals’ prevalent in every other member of the family.
I7.—Geronoceicat Socrnty or Lonpon.
June 28, 1916.—Dr. Alfred Harker, F.R.S., President, in the Chair. The following communications were read :—
1. ‘‘On a new species of Hdestus from the Upper Carboniferous of Yorkshire.” By A. Smith Woodward, LL.D., F-R.S., V.P.G.S. With a Geological Appendix, by John Pringle, F.G.S.
The new fossil described confirms the interpretation of Hdestus as a row of symphysial teeth of an Elasmobranch fish. The row of eight bilaterally symmetrical teeth, fused together, ovcurs at the tapering end of a pair of calcified cartilages, which evidently represent ajaw. An imperfect detached tooth probably belongs to an opposing row. All the teeth are unusually large compared with their base, and the serrated edges of most of them have clearly been worn during life. As in the case of the American Carboniferous Hdestus mirus, small Orodont teeth of the form named Campodus are scattered in the shale near the jaw. Markings on the Hdestus teeth themselves suggest that they have been derived from the Campodus type of
382 Reports & Proceedings—Geological Society of London.
tooth. The specimen, which represents a new species, was obtained
‘by Mr. H. H. Freer from shale below the Rough Rock, in the upper part of the Millstone Grit, at Brockholes, near Huddersfield, and was presented to the Museum of Practical Geology by Mr. E. Crowther.
2. “The Tertiary Volcanic Rocks of Mozambique.” By Arthur Holmes, B.Sc., A.R.C.Sc., D.I.C., F.G.S.
Until recently the district of Mozambique—geographically as well as geologically—was one of the least known of the Kast African coast-lands. During the seasons 1910-11 a prospecting expedition was organized by the Memba Minerals Ltd., and during the second season Mr. E. J. Wayland, Mr. D. A. Wray, and the author visited the country as geologists to the Company.
With the exception of a coastal belt of Cretaceous and Tertiary sediments, flanked on the west by later Tertiary volcanic rocks, the whole territory consists of a complex of gneisses and other foliated rocks, intruded upon by granites belonging to at least two different periods. From Fernao Vellosa Harbour to Mokambo Bay the junction of the sedimentary formations with the crystalline complex is a faulted one, and the volcanic rocks, now greatly dissected by erosion, are distributed on each side of the fault. The lavas are of post-Oligocene age, and are clearly the result of fissure eruptions, the feeding channels being exposed as numerous small dykes that penetrate the underlying rocks.
Throughout the area the prevailing lavas are amygdaloidal basalts, in which the chief amygdale minerals are chlorite, heulandite, and forms of silica. An andesite dyke of later date occurs near the Monapo River. In the north, near the Sanhuti River, picrite-basalt, basalt, phonolite, and sdlvsbergite have been found, and related lavas occurring elsewhere in the area are tephritic pumice and egirine- trachyte. Thus, there occur together, within the limits of a small voleanic field, series of both ‘ alkali’ and ‘ cale-alkali’ types of lavas. The ‘alkali’ series can be closely matched by the lavas of Abyssinia, British East Africa, Réunion, and Tenerife. The amygdaloidal basalts of the ‘cale-alkali’ series are similar to those of the Deccan, Arabia, and East Africa, and also to those (of late Karroo age) occurring in South Africa and Central Africa.
In all, ten analyses have been made, and the variation diagrams constructed from them support the view that each of the series was evolved by a process of differentiation acting on a parent magma. From the composition of the amygdale minerals (which are referred to the closing phase of lava consolidation), it is deduced that the parent magma of the ‘alkali’ series was rich in carbon dioxide, and undersaturated in silica; whereas that of the ‘ calc-alkali’ series was rich in water and oversaturated in silica. The radio-activity of the lavas indicates that the depth from which the parent magma came was probably between 33 and 44 miles from the earth’s surface. The boundary fault along which the lavas are aligned seems to mark a zone where pressure was relieved to an extent and depth sufficient to promote fusion.
Reports & Proceedings—Geological Society of London. 383
Dr. A. Strahan, F.R.S., exhibited cores from borings in Kent, showing pebbles of coal embedded in Coal-measure sandstones. With the coal-pebbles there occurred a few partly rounded fragments of chert, and in one of these Kadiolaria had been identified by Dr. G. J. Hinde. The chert resembled that which had been described from Lower Carboniferous rocks elsewhere. Its occurrence suggested that the sequence of strata had been similar in South Wales and Kent, and taken in connexion with the piping of the limestone surface at. Ebbsfleet and the absence of Millstone Grit in Kent tended to confirm the view that there is unconformity between the Coal-measures and the Carboniferous Limestone in that county.
Mr. F. P. Mennell exhibited a geological sketch-map of the Northern Margin of Dartmoor.
He said that the central part of Devonshire was to a large extent a terra incognita, but, as regarded the fringe of altered Carboniferous rocks along the northern border of the Dartmoor granite, he had been led, in the course of observations originally concerned with the petrology alone, to the conclusion that there was a probability of being able to establish a definite order of succession. ‘This was rendered possible by the occurrence of some well-characterized bands of rock, especially limestones and tuffs, which were exposed in every good river-section. It was true that almost everywhere overfolds, sometimes accompanied by thrusts, were to be detected, and tended to make the observer somewhat doubtful of his ground. Nevertheless, it seemed impossible to escape the conclusion that, as one approached the granite from the north, older and older rocks were met with, and the extremely continuous character of some of the beds seemed to show that, in spite of all minor disturbances, the general sequence could be trusted. The comparison of the different lines of section _ leading up to the moor showed them to be strikingly similar. The granite was, moreover, intruded all along at precisely the same horizon, and its direct offshoots never reached into the lower of the two important bands of limestone, but were confined to the altered shales at the bottom of the series, which afforded, where fresh, good examples of andalusite hornfels. The series, which extends from south of Sourton to Drewsteignton and perhaps right round to Doddiscombeleigh, appears clearly older than the shales which have been so carefully searched for fossils in the Exeter region by Mr. F. Q. Collins. These last are considered of Pendleside age, and nowhere contain any traces of limestone. The probability is thus indicated that the distinctly calcareous series under consideration may represent. part of the Carboniferous Limestone.
It may be noted that, although there are a number of bands of epidiorite representing intrusions of dolerite roughly parallel to the strike of the sediments, the contemporaneous rocks are never of such basic character. The main band of tuff stretches from Lake, near Bridestowe, to beyond Sticklepath, and of the numerous well-preserved rock-fragments it contains, most are of rhyolitic or trachytic character, _ with some which represent altered andesites. __
_ The next meeting of the Society will be held after the long vacation, on Wednesday, November 8, at 5.30 p.m.
384 Obituary—Sir William Ramsay. OBITUARY.
SIR WILLIAM RAMSAY, K.C:B:, LE.D:)D:S8c:,, MD Peep. R85 ECs anare BORN OCTOBER 2, 1852. DIED JULY 23, 1916.
Iv is with sincere regret that we record the death of one of England’s most distinguished scientific men, Sir William Ramsay, who passed away on Sunday, July 23, at his home, Hazlemere, High Wycombe, in his 64th year. He was a nephew of the late Sir Andrew Ramsay, I’.R.S., formerly Director of the Geological Survey (1814-91), and son of William Ramsay, C.E. He was born in Glasgow in 1852, and in its Academy and University he received his principal education. Thence he went to Tiibingen to study chemistry, returning to Glasgow University as Tutorial Assistant in Chemistry (1874-80). He was next Professor of Chemistry and afterwards Principal of Bristol University (1881-7), and finally Professor of Chemistry at University College, London, from 1887 to 1918. His principal researches embraced ‘‘The Molecular Surface Energy of Liquids”, and (in conjunction with Lord Rayleigh) ‘“‘ Argon, a new Constituent of the Atmosphere’”’; Helium, a constituent of certain minerals; also Neon, Krypton, and Xenon (three new atmospheric gases). For his chemical discoveries he received the Davy Medal from the Royal Society in 1895 and (conjointly with Lord Rayleigh) the Nobel Prize in Chemistry in 1904. He is the author of three textbooks of chemistry and The Discovery of the Constituents of the Air, besides many separate papers and memoirs,
At the outbreak of the War Sir William Ramsay at once devoted his great knowledge to the service of our country, and was able to render invaluable assistance to the Government until his health failed some few months since, the malady proving fatal, to the great sorrow of his family and his very numerous friends.
MISCHILELANHOUVUS.-
GxoLogicaL SurRVEY oF SwepreN.—Dr. Axel O. Gavelin has been appointed Director in succession to Dr. Johan Gunnar Andersson. Dr. Gavelin was born in 1875 at Wilhelmina in Lapland, joined the Survey in 1902, and was appointed State Geologist in 1909. He has been acting-head of the Survey during Dr. Andersson’s absence in China.
Caziner PaLfonrotogigvE DE wLInstirur pres Mines ove L’ImpERATRICE CarHERINE II, Prrroerap, Russtr.—We have just received the announcement from Professor Nicholas Yakovleff, Professor of Paleontology in the Institute of Mines, Petrograd, Russia, that on May 5 last, at the Institute of Mines, the ‘‘ Russian Paleontological Society’? was founded by about fifty Russian geologists, paleontologists, zoologists, and botanists. It is the intention of the Society to publish an annual volume in which will appear smaller articles of general interest, and it has also in view the publication of paleontological monographs which will be printed separately.
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ORIGINAL ARTIC ee
I.—Tse Buitpine vp or tHe Norra Ariantric TERT C PLATEAU.
By LEONARD HAWKES, M.Sc. (PLATE XVI.)
T is many years ago since Sir Archibald Geikie pointed out that the Tertiary basalts of the Western Isles of Scotland and North- East Ireland were remnants of plateaux built up of lavas extruded from fissures after the manner described by von Richthofen. In historic times fissure eruptions have taken place in Iceland, and in Zhe Ancient Volcanoes of Great Britain a chapter is included on ‘The Modern Volcanoes of Iceland as illustrative of the Tertiary Volcanic History of North-Western Europe” (1, p. 260). Whilst little remains to be added in support of the very definite analogy exhibited in the nature of the lava streams themselves, the equivalent of the thin bands of red rock so typicaliy intercalated in the 'lertiary series has not been particularly examined, and I have visited Iceland in order to study the red beds themselves and search for their counter- parts in the modern lava deserts.
THe Tertiary Series oF Icenanp.
_ The Tertiary rocks of Iceland are similar in kind to those composing the volcanic series of the same age in the British Isles, only the development is on a much grander scale. The observable thickness is 11,000 feet, and how much has to be added on to this, top and bottom, it is impossible to state. The formation consists chiefly of basic rocks. In the east of Iceland acid types are largely developed, attaining im some places a thickness of 2,000 feet. Wherever I have studied them these acid rocks are dominantly extrusive in character. Occasionally remains of plants and trees together with considerable thicknesses of tuff and weathered material occur between the basalts, but these deposits are not particularly under discussion here. Analogous rocks compose the zone separating the upper and lower lavas in North-Kast Iceland, and their significance has been fully treated of in a recent memoir (2). Owing to their economic importance and plant-remains these beds have attracted most attention, but they occur only rarely in the series, the normal development of which is a succession of basalts separated by thin bands of bright-red rock.
A detailed examination of a thousand-foot section at Begisa, Hyjatjord, North Iceland, showed thirty-eight basalts and partings
DECADE VI.—VOL. III.—NO. IX. 25
an lnStiz UY 2% oN
“tional wuse®S
;
886 Leonard Hawkes—Building up the North Atlantic
of red rock, which gives an average thickness of 26 feet for each flow and its accompanying parting. Two flows were 55 feet thick, one was 6 feet, and one was seen to thin out altogether. The basalts preserve a constant thickness for great distances, but when they thin out they do so rapidly. The interbasaltic layers are composed of a soft colloidal rock a few feet in thickness (commonly two or three feet) and of the variable chemical composition characteristic of the members of the laterite group of rocks. In the present discussion these beds are referred to as ‘ red partings’ to distinguish them from the more varied deposits occurring at rarer horizons.
The prevalent view with regard to these red partings has been expressed by Sir A. Geikie, writing on the Antrim plateau: “It” (i.e. the red interbasaltic layer) ‘‘may be looked upon as probably furnishing evidence of the lapse of an interval sufficiently extended to permit a considerable subaerial decay of the surface of a lava-sheet before the outflow of the next lava” (1, p. 204). Some, on the other hand, advocate the original tuff nature of the red rock, and, as — is pointed out below, this question is of some importance when we attempt to read the history of the Tertiary volcanic period. Thoroddsen writes of the Icelandic series: ‘‘ Der Aufbau des grossen Plateaus hat ungeheure Zeit beansprucht. Dass die Lavastrome nicht unaufhaltsam tbereinander geflossen sind, ist unter anderen aus den zwischen den Basaltdecken befindlichen Verwitterungsprodukten ersichtlich’’! (8, p 232). In the latter part of this paper an attempt is made to indicate more definitely the solution of this problem.
Tue Rep Parrines.
As a rule it is only by microscopical examination that the original tuff or lava nature of the red rock can be determined. | Its colloidal character makes the preparation of thin slices difficult, though good results can be obtained by using petroleum as a lubricant instead of water. Professor Amund Helland has described thin sections of similar Icelandic rocks, but his paper, written in Norwegian, has escaped notice in Britain (4). Several sections were made of specimens taken at random from the Tertiary series. That shown in Pl. XVI, Fig. 1, is of a less weathered rock than usual, and the nature of the parent rock is clearly indicated. A complete petrographic description is not given here, as it is only desired to draw attention to one important point in connexion with the process of palagonitization.
The bulk of the material shown in the section is volcanic glass; one large piece of scoria is seen at ‘A’. The glass fragments have characteristic smooth-flowing’ outlines, those of the scoria being irregular and hackly. The glass is basic, the freshest being light yellow in colour and forming the central parts of the fragments,
1‘ The building up of the great plateaux has taken an enormous time, That the lava-streams were not poured out one upon another continuously is evident, among other things, from the weathered products found between the basalts.’’
Tertiary Volcanic Plateau. 387
so that the stages in the process of decomposition can be studied by observation to the periphery. The glass becomes brown and red and finally a deep blood-red, this progressive change being accompanied by a progressive increase of refractive index. So far these changes do not affect the homogeneity of the glass, but this condition reaches a limiting point and the glass breaks down. The brown oxide separates into spots, some of which, under a high magnification, are seen to possess asteroid forms. The glass cover was taken off the section, which was placed in a saturated water solution of nigrocene. In half an hour the brown oxide was stained blue. Then the section was i1mmersed in strong hydrochloric acid for seven hours. The yellow and red colours of the glass were removed. The section was then reimmersed in the nigrocene for two hours, after which the original red and yellow elass was stained blue, the stain intensity being a maximum for the first-named. The class retained its shape, but on probing with a steel point was seen to be plastic. Thus the brown oxide is colloidal, and the glass owes its colour to iron oxide, which can be removed by strong hydrochloric acid. The glass fragments contain occasional crystals of felspar and pyroxene, but these are quite unaltered. This is even the case where the mother glass has been thoroughly broken down and the crystals are left in a matrix of brown oxide.
The most important fact arising out of the petrological inquiry is the resistance offered by the minerals to the weathering agencies and the collapse of the glass. Helland noted how the crystals of felspar and pyroxene remained unaltered in these rocks (4, p. 81). The palagonitization process may work so completely in the glass that it finally breaks down, whilst the felspar and pyroxene crystals remain practically unaffected. Whatever the particular rationale of the palagonitic decomposition process may be, glass is far more readily attacked by it than minerals, i.e. volcanic ash than lava. Of course, _this follows not only from the lesser resistance offered by the non-crystalline material to the decomposing agencies, but also from its fine fragmental nature, whereby the rock is attacked in all parts at once. Seeing that palagonite rock will take far less time to form from ash than lava, the importance of determining the nature of the original material of the red partings is obvious. (Here we are speaking of the main mass of the lava. The thin frothy upper surface layer of some streams would succumb almost as readily as the ash.)
In the rock just described the original ash character of the deposit is easily seen, but in most of the red partings alteration has been so thorough that it is very difficult and often impossible to settle the question by microscopical examination. If the red rock represented weathered lava, investigation in the field would show a passage to crumbling and decomposing lava surfaces, but I have hardly ever seen clear evidence of this in the case of a basalt covered by a red _ parting. As there are two or three hundred such partings in the Icelandic Tertiary series, detailed individual examination is out of the question, but further light on them can be obtained from general considerations.
388 Leonard Hawkes—Buirlding up the North Atlantic
ANALOoGoUS Deposits or tHE Moprern Lava Deserts.
There is no region which better illustrates the conditions under which the greater part of the Tertiary volcanic series of the North Atlantic lands was built up than the great Oda%ahraun desert which stretches in a northerly direction from the Vatna Jokull, and covers an area of over four thousand square kilometres. It is a plateau of lavas, a stony sea out of which the tuff cones loom like islands. Many of the flows have a ropy surface (see PI. XVI, Fig.22): I have never seen such surfaces in the Tertiary series of Iceland, nor do they seem to have been noted in the British Isles—the fact is a curious one. :
In the summer of 1914 a journey was made across the Oda%ahraun to the Askja crater, and four circumstances were noted which have a bearing on the problem of the red partings. These are: (1) the fresh and unweathered nature of the lava surfaces; (2) the almost complete absence of plant and animal life; (3) the lack of water; (4) the dust-storms. The freshness of the surfaces of lavas, the outpourings of which we have no historic mention of, was evidenced by the sound metallic clang of the horses’ hoofs as they picked their way over the uneven ground. The rough (aa) lava surfaces also showed very little evidence of any chemical denudation, though where markedly cindery some mechanical weathering down had produced a black sand. I saw no sign in the Oda%ahraun or in the wastes to the east of Namufjall, Myvatn, of any weathering of lavas giving a product comparable with the red partings. ‘The only equivalent to the latter were the loose fragmental deposits of volcanic ash and sand which covered certain areas. When at rest these deposits are a great boon to the traveller enabling him to make fairly rapid progress over ground that would otherwise be impassable, but they are greatly dreaded when winds arise, being caught up and carried forward as a brown dust cloud. Even in the houses bordering the desert, though door and window be carefully barred, still the fine particles make their way into the room. To quote from Thoroddsen : ‘¢ Blown sand is of varied quality and origin. It may be coarse or finer; it is sometimes so fine that it penetrates everywhere. During violent storms in sandy districts the fine dust is carried to the most. remote quarters of the island and is deposited as a fine layer all over the surface; it even falls on vessels in mid-Atlantic. But naturally most dust falls in districts bordering on the tuff-belt or situated in it, as the dust chiefly originates from the tuff. The atmosphere in distant regions is often yellowish brown because of the fine dust suspended in the air, and this dust cloud is known in Iceland as ‘mistur’. This tuff dust has played a very important part in the formation of the Icelandic soil and subsoil, and it can be demonstrated almost everywhere’? (5, p. 243). .
Tuer INTERPRETATION OF THE Rep PaArtINGs.
It seems that these fragmental deposits are the equivalents of the majority of the red partings, and that these latter do not represent weathered lava-flows. This conclusion has been felt hard of acceptance by some who have been impressed by the lack of
Tertiary Volcanic Plateau. | 389.
fragmental product in, fissure eruptions, but this objection is removed after a study of the OdaSahraun deposits. It must be remembered that there is commonly some explosive action accompanying the extrusion of the lava, although the fragmental material thus formed is much inferior in quantity to the latter., Basic tuff cones 500 metres high have been built up in the Oda%¥ahraun, and by attrition of these and smaller masses the supply of loose material blown about the desert is constantly reinforced. It is not necessary to imagine the red parting to be derived from fragmental material erupted during the extrusion of the underlying basalt; it may belong to an outburst far removed in place and time, or several such. We conceive of these deposits being transported hither and thither over the plains till they happen to be caught and imprisoned by an outpouring of lava. The rising of a wind a few hours before eruption may make all the difference as to whether a basalt is to be accompanied by a tuff or not, and by this interpretation of the red partings we are guarded from attaching too much importance to their occurrence and thickness, which may be purely accidental.’
The flooding of basalts and volcanic sand in the manner postulated has been graphically described by W. L. Watts (6, pp. 148-56), who had a unique view of the last fissure eruption which took place in the ‘ Myvatnsoreefi’ (a northern continuation of the Oda%ahraun) in August, 1875. Sometimes thin bands of acid tuff are intercalated in the red partings. They may be mere streaks an inch thick, standing out by reason of their lighter colour, and remarkably persistent for considerable distances. One band two inches thick in a parting at Seydisfjord contains well-developed crystals of soda- microcline and soda-pyroxene, minerals common in Icelandic acid rocks. In such cases where the bands are purely acid and contain no basic material they obviously result from a contemporaneous eruption, and it is also clear that the palagonite rock above them is material
_ blown from a distance.
There is one feature that distinguishes the dust deposits of the modern Icelandic deserts from their Tertiary equivalents, and that is their colour. The dust is usually brown, but I have never observed the bright-red tint so characteristic of the old red partings. The colour of these Tertiary rocks is generally taken as an indication that they were formed under warmer climatic conditions than obtain in Iceland at the present day, but that this is not acomplete explanation will be evident from the following extract of a letter I received from Professor Thoroddsen in January, 1914: ‘‘You will see the red beds almost everywhere in the basalt formation, but not only there; they are also common between the younger dolerite flows which are striated, and probably were outpoured during the Ice Age. I have not done any special investigation of these red beds, but I think they most frequently must be deposits of volcanic ash, and seldom resulting
1 “*Tf the occurrence and thickness of this layer’? (i.e. the interbasaltic red parting) ‘‘ could be assumed as an indication of the relative lapse of time between the different flows of lava, it would furnish us with a rude kind of chronometer for estimating the proportionate duration of the intervals between the gpupuene. (1, pp. 254-5).
390 Leonard Hawkes—Building up the North Atlantie
from subaerial denudation of the vesicular basalt surface like the laterite in India, because in Iceland they are very often found between basalts which have been poured out under the severest arctic climatic conditions.”
The want of water and consequently plant, and animal en is forcibly brought home to the traveller in the Oda%ahraun, as the food which has to be taken for the horses seriously increases the size of the caravan and prevents any long absence from the grass lands. The lack -of plant and animal remains in the Tertiary red partings, which before had presented a rather pnzzling feature, is quite understood. Rivers hardly exist on the Oda%ahraun proper. The snows of the Dyngjufjoll, a ring of tuff mountains arising out of the desert, give birth to a few streams which soon lose themselves in the holes and gjds of the lava. The general absence of river courses and deposits in the Icelandic series, and indeed of the North Atlantic Tertiary volcanic series, is to be expected. Sir A. Geikie has described deposits and cuttings in the plateau of Western Scotland, due to rivers which are compared with those traversing the Icelandic desert of the present day (1, p. 229). In this connexion it must be remembered that practically all these rivers originate in the great Jokulls, and we have little evidence that ice-caps existed in Iceland in Tertiary times.'!. Even these Jokull rivers flow, not over the lava deserts, but rather over the sand and glacial deposits covering large tracts in the interior of the island, regions more representative of the thick interbasaltic series than of the red partings. The rivers which flowed over the Scottish plateau had their sources in the Western Highland mountains, which provided a large catchment basin sending forth rivers of such a size that they did not readily peter out on reaching the lava plains, but there is no evidence of any such high land bordering the Iceland region.
During the building up of the greater part of the North Atlantic volcanic series-we conceive of immense lava plains, covered in places by loose fragmental products. These latter did not always remain stationary, but were liable to be caught up by the wind and carried long distances before being redeposited as a thin mantle covering large areas. This loose material was thrown up during the eruptions and also originated through abrasion of the tuff cones scattered over the plain, and in a subordinate degree from weathering of the scoriaceous surfaces of the lavas. In all probability these plains connected the New and Old Worlds, but commonly there was a dearth of rivers, plants, and animals, and no migration of these latter. At rare intervals vegetation gained a foothold, and ‘‘it is not _
improbable that the basalt plateaux might even be densely wooded ”’
1 Dr. Pjetursson has grouped the top series of the Tertiary basalts together as a ‘‘Graa Etage’’, and in them he has discovered ice-scratched surfaces which have led him to advocate the hypothesis of a ‘‘ Tertiary, possibly early Miocene Ice Age” (7, p. 99) The evidence is as yet too meagre for this hypothesis to be accepted with any certainty, though without postulating a change in absolute mean temperature it would be quite reasonable to imagine that glaciers were formed during the latter part of the volcanic period, eoneeunene upon the elevation of the plateau through successive outpourings of lava.
Tertiary Voleame Plateau. 391
(8, p. 241), though it is unlikely that this condition obtained over the ‘land-bridge’ in its entirety at any one time; it is more reasonable to conceive of temporary oases, limited in extent, themselves migratory.
Toe TIME REPRESENTED BY THE Rep Parrrnes.
If the red partings are regarded as weathered lavas it must be recognized that they represent the lapse of a considerable interval of time, for even if they originated under climatic conditions similar to those which obtain in India to-day the growth of the Indian laterite is exceedingly slow. But if these partings are weathered tufts, which from examination in the field and laboratory, ,and also by analogy from the deposits of the modern desert of the Oda%ahraun, would seem to be the rule, the length of the inter-eruptive period is considerably diminished for two reasons. One is that, as has been pointed out above, volcanic. ash is far more readily attacked by the palagonitic decomposition process than lava, and the other is that the red parting covering a lava may represent material which had been thrown out and blown over the plains long before the outflow of the lava with which it is ultimately associated. Thus we could conceive of two flows extruded in one week being separated by a parting. This is an extreme case, but we have definite evidence that the duration of the period represented by the red partings was relatively short.
At the entrance to the Seydisfjord (Hast Iceland), between Dalatangi and Shalanes, acid and basic rocks are exposed in a magnificent cliff section which has been figured by Helland
(4, fig. 10). The main mass of the acid rock is a plano-convex shaped lens of liparite with a maximum thickness estimated at 300 feet, resting on, surrounded, and overlain by an almost horizontal series of basalts and red partings. Underlying the whole of this is _ a thickness of acid tuff and breccia. The cliff-face is almost vertical, and it was impossible to examine much of the section with the hammer. At one place it was found that the thinner lower exposure of acid rock is a green tuff-breccia, rudely stratified, and containing blocks of basalt and banded liparite up to 2 feet in length. ‘I'he thick main mass of liparite is a fine-grained greyish rock with prominent flow-banding. At its lower boundary it passes into a black obsidian about 14 feet thick with a breccia-like under-surface. As far as could be seen this obsidian band composes the periphery of the liparite throughout the section, with the exception of the eastern portion, which has been denuded away. The most interesting part of the mass is its western termination, and as it was not possible to land at that point I had to be content with making a sketch which is reproduced in Fig. 3. The relations of the basalts and red partings to the obsidian margin of the liparite are clearly shown. The former retain the approximate horizontality which characterizes the whole of the bedded basalts of the cliff section. The liparite is extrusive, as shown by— 1. The undisturbed basalts. 2. The nature of the junction of the obsidian and basalts iilusteated
392 Leonard Hawkes—Building up the North Atlantic
in Fig. 8. It would be impossible to conceive such a regular curved © boundary to result if the liparite were intrusive. The marked sagging of one of the basalts at 7’ is very suggestive of a lava flowing round a hill. We have clear evidence of an acid outbreak in the vicinity before the extrusion of the main mass in the lower tuff-breccia, and our conclusion is strengthened by the similarity of this flow to the post-glacial acid flows of the Torfajokull district described by Thoroddsen (9 and 3, p. 155). These lavas are in the main composed of a bluish-grey rock with flow-banding and occasional columnar structure, and grade at the periphery first into obsidian and finally into pumice. The Hrafntinnuhraun stream is a light-grey rock 40-50 feet thick, with an outer shell of obsidian 5-10 feet thick and a final 2-8 feet thick casing of pumice (9, p. 612). The Seydisfjord liparite was a surface flow. It formed an eminence on the plain, being gradually surrounded by successive basalt lavas and finally submerged by them. Estimating the liparite as 300 feet in maximum thickness and taking 26 feet as the average thickness of the basalts, twelve of the latter were required to cover it.
55
Ca. 80ft.
€--------
Fic. 3.—Section, western end of the liparite exposure, Shalanes, Seydisfjord. F' = fault throwing two or three feet; ZL = liparite; O = obsidian border to L; B= basalt; & = red parting.
The most important feature is the undenuded character of the liparite. There is no sign of any debris round the hill, and the outer obsidian shell remains intact. The readiness with which lparite is broken up, especially in comparison with basalt, is well known and abundantly illustrated in East Iceland, where basic and acid rocks are so intimately associated and attain such wide development. Acid rocks are fissile and brittle, constantly breaking up and forming scree slopes where no plants gain a footing owing to the ever falling stream of blocks, but the tough basalt is much more resistant and its scree slopes are typically green mantled. Whilst obsidian is more resistant than liparite and provides a protective sheath for acid lavas (8, p. 158) the unaltered form of this Seydisfjord flow shows that no great interval of time elapsed during its submergence by the basalts, and also confirms the conclusions reached above respecting the tuff, or rather original fragmental, nature of the red partings, for how
Tertiary Volcanic Plateau. 393
could twelve basalt surfaces be weathered down whilst the acid rock remained unattacked ??
Duration oF THE Tertiary Votcanic PERIOD.
The investigation of the red partings themselves, the analogous deposits of the modern lava deserts, and the Seydisfjord section, all go to show that no great time elapsed between the outpourings of the majority of the basalts. Is it possible to form any idea of the absolute average period of rest ?
We have the evidence of the voleanic activity in Iceland in historic times, but the record only stretches over a thousand years, and much of it isuncertain in character. Also the relative intensity of vulcanism in Tertiary times and now must be taken into account. When we conceive of the magnitude of the Tertiary outpourings which probably obtained right across the North Atlantic, forming a land-bridge connecting the Old and New Worlds, and then consider the modern outflows covering what is relatively a very small area, we appreciate the great diminution of activity. It is quite reasonable to suppose that vuleanism so stupendous should, at any particular place, have been manifested more frequently than in the restricted area which has witnessed volcanic activity in historic times. At the last fissure eruption in the Myvatnsorcef{, in 1875, lava was poured out five times from various parts of the fissure (10, p. 139). In August of that year Watts observed the flooding of the stream of the preceding April (6, pp. 154-5).
Taking all the evidence into consideration, it seems that a thousand years would not be an improbable estimate for the average duration of the inter-eruptive periods represented by the red partings. That this is a liberal allowance will probably be conceded on consideration of what it means in the case of the Seydisfjord section described above, i.e. that in 12,000 years the acid flow suffered no marked
amount of denudation. Leaving out of count the longer rest intervals, with the known thickness of the Tertiary formation 11,000 feet, and taking 26 feet as an average basalt thickness, we arrive at a period of approximately half a million years for the building up of the series. It is impossible to say what interval of time is represented by the
1 These observations are of interest with respect to former discussions on the difficult problem of the age of the Antrim rhyolites. Considering the question of their intrusive or extrusive origin Sir A. Geikie writes: ‘‘ The rhyolite has been supposed to form the summit of an ancient volcanic dome, perhaps of Eocene age, which had been worn down before the outflow of the plateau- basalts under which it was eventually entombed. Had this been the true history of the locality it is inconceivable that of a rock which decays so rapidly as this rhyolite, and strews its slopes with such abundance of detritus, not a single fragment should occur between the successive beds of basalt which are supposed to have surrounded and buried it. . . . Yet it is clear from the upper surfaces of some of these lavas that a considerable interval of time separated their successive overflows, so that there was opportunity enough for the scattering of rhyolite-debris had any hill of that rock existed in the vicinity ’’ (1, p. 428). The relationship of the basalts to the rhyolites in Antrim is very obscure, but in the Seydisfjord section the extrusive nature of the acid rock is quite clear, and arguing from its undenuded surface we conclude that relatively no great interval of time elapsed during the outpouring of the basalts.
394: L. Hawkes—WN. Atlantic Tertiary Voleanre Plateaw.
rare long periods of quiescence, but there is no evidence that that would be of a different order of magnitude from that required for the rest of the series, and reckoning this interval as as much again we obtain a figure of one million years for the building up of the whole volcanic formation.
What impresses the student of Icelandic geology is not so much the great time which elapsed during the accumulation of the Tertiary series, but rather the long period necessary to allow of the enormous denudation which has obtained. Sir A. Geikie has emphasized this latter point with reference to the British and Ferode Islands: ‘‘ Among the more impressive lessons which the basalt-plateaux of North- Western Europe teach the geologist, the enormous erosion of the surface of this part of the continental area since older Tertiary time takes a foremost place” (1, p. 455), and from observations on Mull this interval is estimated at twelve million years. For the present purpose this may be taken as a general figure for the whole North Atlantic plateau, although the application to Iceland of the methods by which it was obtained would show a greater interval.
Whilst in absolute amount we can have little confidence in the figure of one million years given for the building up of the plateau, and that of twelve million years estimated for its degradation since the Tertiary volcanoes became extinct, the relative proportion shown by these figures would seem to be correct in kind, if not in degree. When we investigate the Tertiary series of Iceland with respect to the conditions under which it was built up and see how it has been tilted, faulted, and denuded, one fact is clear, and that is, the relative smallness of the time interval which was consumed in building compared with that which has elapsed subsequently—this conclusion doubtless applies to the whole of the North Atlantic plateau. It must be remembered, however, that the dislocation and denudation of the plateau began long before the close of Tertiary times—indeed, the major part was completed before the advent of the Glacial Period.
One of the hindrances in the way of a better understanding of the old Icelandic series is the lack of ‘horizons’. It is certainly remarkable that definite horizons should be wanting in such an enormous thickness of rock. The Tertiary volcanic formation is probably unique in this respect amongst all the post-Archzan rocks of the Atlantic countries. The explanation is to be found in the rapidity of building. Per unit of thickness the Tertiary volcanic series represents the smallest time of accumulation of all the post- Archean formations.
In conclusion, I wish to express my great indebtedness to Professor G. A. Lebour for assistance and encouragement in the carrying out of this investigation, and also to Professor V. M. Goldschmidt, of Christiania, for guidance in the petrographic work.
REFERENCES. 1. Sir ARCHIBALD GEIKIE, The Ancient Volcanoes of Great Britain, vol. ii, 1897. 2. The Interbasaltic Rocks of North-Hast Ireland (Memoirs of the Geological Survey of Ireland), 1912. 8. TH. THORODDSEN, ‘‘Island. Grundriss der Geographie und Geologie ”’ : Erginzungsheft No. 152 zu Petermanns Mitteilungen, 1905.
Grou. Maa., 1916. Prats XYI.
Fic. 1. Thin section of a red parting, x 35 diaim., Begisa, Eyjafjord, North Iceland.
Fig. 2. Ropy Lava, from the Odddahraun, Iceland.
Dr. A. Morley Davies—Oxford and Ampthill Clays. 395
4, A. HELLAND, ‘‘ Studier over Islands Petrografi og Geologie’’: Arkiy for Mathematik og Naturvidenskab, Kristiania, 1884, p. 69.
5. TH. THORODDSEN, ‘‘ An Account of the Physical Geography of Iceland, with special reference to the plant life’’: The Botany of Iceland, pt. i, 2, 1914.
W. LL. Watts, Across the Vatna Jékull, London, 1876.
. HELGI PJETURSSON, Om Islands Geologi, Kébenhayn, 1905.
. JAMES GEIKIE, ‘‘ On the Geology of the Ferée Islands’’: Trans. Roy. Soc.
Edin., vol. xxx, pt. i.
. TH. THORODDSEN, ‘‘Om nogle postglaciale liparitiske Lavastromme
i Island’’: Geol. Foren. Férhandl., Bd. xiii, p. 609, 1891. 10. Hans SpPETHMANN, Islands grisster Vulkan: Die Dyngjufjoll mit der Askja. Leipzig, 1913. EXPLANATION OF PLATE XVI. Fic. 1.—Thin section of a red parting, Begis4, Eyjafjord, North Iceland. x 35 times nat. size., >, 2.—Ropy lava from the Odadahraun.
Go ws
I[.—TuE Zones oF THE OxForD anp AmprHitt Crays In Buckine- HAMSHIRE AND BEDFORDSHIRE. By A. Morey Daviss, A.R.C.S., D.Sc., F.G.S.
HAVE been studying the zones of the Upper Jurassic clays for the i. last seven or eight years. Repeated delays from various causes have already diminished the value of the results, and as the work is now held up indefinitely it seems advisable to publish a summary of the conclusions to which I have come, in case the completion of the work may fall to other hands. Such a summary must necessarily be: much more dogmatic than I could wish. I have to acknowledge my very great indebtedness, both direct and indirect, in connexion with this work, to Mr. 8. 8. Buckman.
1. Lower ornatum (jason or elizabethe) zone.—The lowest zone with which I have met is that characterized by crushed iridescent ammonites, largely of the genus Cosmoceras, which are abundantly represented in museums from the railway cutting at Christian Malford, Wilts.1. This zone was also recorded at T'rowbridge, Wilts.’ It is well shown at Itter’s brickworks, Calvert station, Charndon (Bucks), and at several brickworks at Wootton Pillinge (Beds). It seems also to be present in the Peterborough district, at Dogsthorpe,
to judge by specimens I have been shown. - 2. Hitherto, in England, no clear distinction has been drawn between the above zone and a higher “‘ ornatum zone”? with equal abundance of Cosmoceras but in which the fossils are pyritized. In Bavaria, however, the two are separated by a zone with a very different and well-marked fauna *—Cosmoceras castor (Reinecke), C. pollux (Rein.), Phlycticeras pustulosum (Rein.), and species of Erymnoceras (the true coronatc). Traces of this zone may be shown by the occurrence at Trowbridge, Calvert,* and Wootton Pillinge of
1S. P. Pratt, Ann. Mag. Nat. Hist., viii, pp. 161-5, 1842.
2, R. N. Mantell, “* Strata exposed in the cuttings of the Branch Railway . . . through Trowbridge’: Q.J.G.S., vi, pp. 312-13, 1850.
° L. Reuter, Ausbildung des Oberen Braunen Jura im Nordlichen Teile der Frinkischen Alb (Miinchen, 1908), pp. 75-81.
+S. S. Buckman, ‘‘ Kelloway Rock of Scarborough’’: Q.J.G.S., lxix, p. 159, 1913.
396 Dr, A. Morley Davies—Zones of the
Erymnoceras reginaldi (Morris) in the upper part of the section ; but the most typical members of the faunaare quite unknown in England. Possibly, two zones should be recognized, only the lower (coronatum zone) being found in England.
3. Upper ornatum or duncani zone.—This is the zone with pyritized ammonites, mainly Cosmoceras spp. and Perisphinctes spp. It is seen at Summertown (Oxford) and at many pits in the Peter- borough district, e.g. Eye Green. In Bucks and Beds I have not yet found it, except doubtfully at Woburn Sands. ‘The total thickness of the ‘‘ ornatum zones’’ is very considerable, and several minor divisions might be distinguished, corresponding generally to those recognized by Judd in the Peterborough district.!. The Wootton Pillinge district seems to offer the best opportunity of working these out.
4. Athleta zone.—The clays which I place in this zone are deficient in ammonites. They contain <Aulacothyris bernardina (VOrbigny) and abundant Gryphee which may be identical with G. bilobata, J. de C. Sowerby, though after examining a very large number of Upper Jurassic Gryphee I hesitate to give a definite specific name to any. In the two places where I have seen these beds exposed—Ludgershall railway cutting and Eastman’s brick- works, Woburn Green—they underlie the well-marked renggeri zone. At my last visit to Woburn Green (in July, 1914) I saw one ammonite that suggested that the section penetrated down to the duncani zone below, but I was too much occupied with the higher beds (usually quite inaccessible, but then most fortunately measurable in detail) to have any time to examine fully the lower part. Nowhere else have I seen any evidence of the superposition of this zone on any other.
5. Renggert zone. — This zone was well exposed during the excavation of the Ludgershall railway cutting (Great Western Railway, direct Birmingham line). It is also shown in the upper part of the Woburn Sands brickworks, at a small excavation at Aspley Guise (opposite the first houses up the hill from the railway halt), and at the brickfield at Sandy, Beds. From the large collection of fossils from Ludgershall it is possible to state that the fauna is essentially that of Liesberg in the Bernese Jura,’ with certain interesting minor differences :—
(1) The absence of Phylloceras. It is well known that this Mediterranean genus only occurs sporadically in Central Europe and Britain, and less frequently in the latter province than in the former. No Phylloceras is known in Britain above the Upper Lias.
(2) The much greater abundance and variety of forms of Quenstedticeras, indicating boreal affinities.
(3) The Oppelid Zaramelliceras episcopale is represented in the Bernese Jura by its typical form only ; in the Ledonian Jura (farther south) it is accompanied by the thicker variety globoswm, but at Ludgershall thinner varieties predominate.
(4) Cosmoceratids are not found in the Bernese and Ledonian areas; in more northern areas the last species of this family still
1 J. W. Judd, Geology of Rutland (Mem. Geol. Surv.), 1875, pp. 232-6. 2 P. de Loriol, Mém. Soc. Pal. Suisse, xxv—xxvii, 1898-1900.
Oxford and Ampthill Clays. 397
survived. ‘his is the case not only in England but in Normandy,' and perhaps in South Germany (to judge from some of Quenstedt’s figures).
Mr. Buckman has distinguished a lamberti zone below the renggert zone,” but the evidence on this head is unsatisfactory. There were in the Ludgershall cutting two bands of soft earthy limestone, one highly fossiliferous, the other not. ‘he former contained large specimens of Quenstedticeras sutherlandie (d Orbigny) and Peltoceras spp. The air-chambers of these fossils are filled with rock-matrix, and the casts are sometimes overgrown with serpule and bryozoa, and have been subject to wear and tear subsequent to this encrustation. They certainly indicate a different fauna from that of the renggeri clays, but I collected the renggeri fauna from below as well as above the stone-beds, although as the collecting was made on a sloped surface the fossils may have come from above. At Woburn Sands two exactly similar beds (called elunch by the workmen) are found, and here I am quite sure that the renggerd fauna occurs in situ below as well as above the clunch. The fossils in the clunch, however, are not the same as at Ludgershall. Thus there are several puzzles to be cleared up before we can decide whether the differences of fauna indicate difference of age or difference of conditions.
6 and 7. Vhe pre-cordatum zone.— This term was used by Mr. Buckman® as a provisional name for the uppermost beds of the Oxford Clay, containing ammonites in some respects intermediate in , character between Quenstedticeras and Cardioceras, having ribs with less geniculation, less tuberculation at the peripheral margin, and less of a forward sweep on the periphery than in the latter genus. Such are Nikitin’s species,* rotundatus, rowillert, vertebralis, tenurcostatus, quadratoides, Lahusen’s nikitinianum, and possibly his cordatum and excovatum in part, and de Loriol’s*® C. cordatum vars. B to F (perhaps var. A also).
More recently Mr. Buckman has used the term ‘‘ scarburgense zone”’ in place of ‘‘pre-cordatum zone’’.6 There seem, however, to be at least two zones distinguished by ammonites of this general type. In the lower there are fairly stout species of the quadratoides type, preserved as pyritic casts; in the higher, thinner forms with finer ribbing (tenwicostatum type) occur with shell preserved. Both zones contain large examples of Gryphea dilatata, auctt.
The lower pre-cordatum zone was exposed in ditches on the low ground between Woodperry and Studley, at the brick-field south-east of Studley, in the Great Central railway cutting north of Wotton station, and at the brickfield close to Quainton Road junction. How far it may correspond to any of Mr. Buckman’s Yorkshire zones
1 Z.. Brasil, Bull. Soc. Géol. Normandie, xvii, pp. 36-49, 1896.
2 §. S. Buckman, op. cit., p. 159.
3 In Lamplugh & Kitchin; Mesozoic Rocks in Coal Explorations in Kent (Mem. Geol. Surv.), 1911, p. 132.
4 S.N. Nikitin, Jura Ablagerungen zwischen Rybinsk, Mologa und Myschkin an der oberen Wolga (Mém. Acad. Sci. St. Petersburg, xxviii, 1881).
> Op. cit., xxv, pp. 14-22.
§ Q.J.G.S., lxix, pp. 157, 159, 1913, and in Geology of . . . Whitby and Scarborough (Mem. Geol. Sury.), 1915, pp. 60, 87.
398 Dr. A. Morley Davies—Zones of the
(vertumnus, gregarium, vernon) I am unable to say, nor can I venture ut present a correlation with the late M. Robert Douvillé’s sequence at Dives.’
The. higher pre-cordatum zone (perhaps answering to Mr. Buckman’s scarburgense zone) has been exposed in a well-sinking near Studley? and in the Great Western railway cutting immediately north of the tunnel in Rushbeds Wood, Brill. In both these cases the ammonites recorded as C. cordatum were finely ribbed forms of the tenurcostatum type.
8. The cordatum or vertebrale zone.—The zone in which the true Cardioceras. cordatum (J. Sowerby) occurs is only represented in the district under immediate notice by the Arngrove Stone or Rhazella- chert, but westwards it is well represented by part of the Lower Caleareous Grit. The bcarmatum zone which follows it in the Abingdon district is not found at all to the east.
9. The martelli zone (plicatilis zone, auctt.).—This is the Upper Corallian of the areas where the coral facies is developed. Apart from its characteristic perisphinctid ammonites, it 1s recognized by the abundance of Hxogyra nana (J. Sowerby) * in its lowest beds. The calcareous facies of these beds is seen as far east as Wheatley, beyond which there is a sudden change into Ampthill Clay. The basement beds characterized by great numbers of /. nana were observed and mapped long ago by Polwhele, and recently by H. B. Woodward, but the finest exposures of them were obtained still later in the railway cuttings at Ashendon junction and Dorton. Here they consisted of varying beds—bluish clay, white limestone, and marly beds full of brown oolite-grains. Some of the latter closely resembled the Elsworth rock except that they were unconsolidated; others, by the abundance of oysters and serpule, approached in character the Gamlingay basement bed. Plentiful radioles of Cidaris smithi, Wright, with a few of C. florigemma, Phillips, inked them with the caleareous beds to the west. They were overlain by over 30 feet of drab clay with beds of soft argillaceous limestone, the clay yielding oysters of the deltoidea and discordea types, the stone-beds Perisphinctes chloroélithicus, Giimbel, and other maréelli-zone fossils. In short these railway cuttings link up Polwhele’s clay in the most satisfactory manner with the typical Ampthill Clay and its basement beds, including the Elsworth Rock.
‘Neither Seeley nor Roberts, to whom we are indebted for most of our knowledge of the Ampthill Clay, seems to have questioned its equivalence to the whole of the Corallian. Mr. C. B. Wedd, by his discovery of Elsworth Rock as a base to the Coralline Oolite of Upware, made it highly probable that the Ampthill Clay is Upper Corallian only. H.B. Woodward was cautious in his correlation. He wrote of the abrupt termination of the Corallian stone-beds at
1 Cardiocératidés de Dives (Mém. Soc. Géol. France), 1913.
2 Davies, Q.J.G.S., lxiii, p. 40, 1907.
3 Davies, Proc. Geol. Assoc., xx, p. 185.
4 The holotype of H. nana came from the Lower Kimmeridge Clay of Shotover. Should the much commoner Corallian form prove distinct from this, it would probably take the name Haogyra mima (J. Phillips).
*° C. B. Wedd, Q.J.G.S., liv, pp. 614-16.
Oxford and Anpthill Clays. 399
Wheatley: ‘(This termination has been attributed [by Sedgwick, Fitton, and Hull] to the unconformable overlap of the Kimeridge Clay, but the evidence favours the view that the rock-beds may be largely represented in point of time by sediments of an argillaceous character.” }
The truth now appears to lie between the two views here referred o. ‘There is an ‘‘ unconformable overlap’’, but of the Ampthill Clay, not the Kimmeridge Clay, and over the Lower Corallian. Farther east the break becomes greater. The Arngrove Stone is first over- ‘stepped; in the Great Western railway cuttings the Hzogyra nana beds rest on the upper pre-cordatum zone; at Quainton Road station typical Ampthill Clay with Ostrea discoidea, Kitchin, forms the floor of the goods-yard, while the /ower pre-cordatum zone is exposed in the old brickfield at the same level half a mile to the north-west. I am unable to say which of the pre-cordatum zones comes below the Ampthill Clay at Ampthill. At Sandy the Avogyra nana beds form the top of the brickfields section (a fact that has hitherto escaped notice) and rest upon the rengger? zone.
The gradual overstep of the Oxford Clay zones by the Ampthill Clay is indicated diagrammatically in the accompanying section. If this is compared with the diagram given by Lemoine? or those by Reuter,* it will be seen that a martelli-zone transgression is a phenomenon common to England, North-East France, and Bavaria.
Wheatley Ashendon Junc* Ampthill Abingden | Arngrove \ Quainton : Meat Sands Saat j | | ! | | | | \ ht 1 | | i (ems | | | \ \ \ bent \ nae ie \ J 1 1 E Coralia Sartell” Zones Ampthill Clayzae= hawt aca: = FESS IS. Be ape =e as, es = ——s ; Se oe COL [o) Ape up See ZF, EE ASIA Z
Diagram section along the outcrop of the Coral Rag and Ampthill Clay in Bucks. and Beds. Horizontal scale approximately 15 miles to an inch. Thick- nesses of zones are entirely diagrammatic. The line of crosses marks the: regions where the basement beds of the Ampthill Clay have been observed. L.C.G.=biarmatum zone in Lower Calcareous Grit.
What follows the martellc zone I am unable to say. There is. a distance of only 700 yards between the Great Western railway cutting where the Ampthill Clay was most fully exposed and the- brickfield described by me in 1907‘ and by Messrs. H. B. Woodward and Lamplugh in 1908.° The latter authors placed the lower beds of
1 Jurassic Rocks of Britain (Mem. Geol. Surv.), vol. v, pp. 133-5. 2 Géologie dw Bassin de Paris, 1911, p. 103, fig. 52.
3 Op. cit., Textbeilagen H, J.
2 Q.J.G.S., lxiii, p. 30, 1907.
> Geology of Oxford (Mem. Geol. Surv.), p. 44.
400 _ Dr. Du Riche Preller—Contact-Zone of
the brickfield in the Ampthill Clay, but with that I cannot agree. The lowest beds normally exposed in the brickfield belong to a zone which has always been counted in England as part of the Kimmeridge Clay—the zone we have been accustomed to call alternans zone, but which Dr. Salfeld has told us is wrongly so called (provisionally I would call it the serratum zone). Sixteen years ago I saw deeper beds of clay exposed at the brickfield (in the foundations for the chimney-stack), but I did not recognize any of the beds in the railway cutting as identical with these. ‘here must therefore be some thickness of clay outcropping in the 700 yards between the two exposures, and this may include the representative of Dr. Salfeld’s warte zone."
The mapping of zones along the outcrop of a thick mass of clay is not an easy matter through an inland area, mainly grass-land, but it may be of some practical value. The clays of different zones are not of equal value tor brickmaking, or at least not equally suitable for particular processes; and in the selection of a site for new works some means of determining which type of clay will be found at a suitable depth must be desirable. Such a means may be found in a zonal map.
IlI.—THe Contact-Zonr oF THE ALPS AND THE APENNINES IN Western Liguria.
By C.S. Du RicHE PRELLER, M.A., Ph.D., M.I.H.E., F.G.S., F.R.S.E. I. Iyrropucrory.
N a paper on the Permian formation in the Maritime Alps, etc. (Guot. Mac., 1916, pp. 7-17), I mentioned incidentally that
it extends from those Alps, viz. from the Montgioie range east into Liguria as far as the Savona Hills. As in the former so also in the latter region, that formation is composed of essentially gneissic schists known as apenninites or besimaudites belonging to the Lower Permian or Permo-Carboniferous, and of sericitic schists, quartzites, and clastic rocks or ‘ anagenites’ which constitute the Upper Permian or Verrucano proper, forming a transition to the Lower Trias.” The geological limit of the Permian in the Savona Hills coincides more or less with the geographical line of division of the Alps and Apennines at the Colle or saddle—also called Bocchetta—d’Altare; but another geological line of division exists still further east, at the junction — of the Triassic and Eocene formations in the Chiaravagna Valley near Sestri Ponente, immediately west of Genoa. In reality the geological division is marked, not by either of those lines but by a contact-zone between them. This contact-zone occupies the whole of Western Liguria and comprises two distinct and dissimilar parts: one, the Triassic cale-schists and pietre verdi area or Voltri group, which extends for about 25 kilometres along the Riviera littoral west of Genoa from Sestri Ponente to Voltri, Varazze, and Celle Ligure,
INQ? -Gist, xix, p. 42371913.
2 This division has its exact equivalents in the Apuan Alps or Carrara Mountains as the lowest formation underlying the marmiferous Trias, and in the Verrucano—a name derived from Monte Verruca—of the Pisan Hills.
the Alps and Apennines in Liguria. 401
and the other or Savona group, which skirts the littoral for about 15 kilometres from Celle to Savona and Zinola, and is composed for the greater part of a crystalline massif of granitic, gneissic, and amphibolic rocks.
Both these self-contained groups present respectively geological features entirely different from those of the adjacent areas east and west. Having examined them both some years ago, I propose to confine the present paper to the crystalline massif of Savona, which, owing to its altogether abnormal position and composition, is of absorbing interest, and has within recent years been the subject of remarkable interpretations as an overthrust zone par excellence. The Voltri group I propose to consider in a future paper in connexion with the adjoining ophiolithic area of Eastern Liguria.
II. Generat Fraturss. (Fig. 1.)
The Savona Hills form approximately a rectangular area about 15 and 10 kilometres in length and width or 150 square kilometres, its general direction being south-west to north-east. On the south a rugged, craggy wall of gneiss runs along the coastline with some intervening Pliocene deposits at Celle, Albissola, Savona, Fornacci, and Zinola. On the west it skirts, from the coast upwards, the Permo-Carboniferous formation to Quiliano, Roviasca, Monte Curlo, and the village of Altare, a commanding point on the divide between Liguria and Piémont, at about 600 metres altitude. Thence, on the north, it follows the crest-line of the Apennines to Mte. Castlas (851m.), Mte. San Giorgio (840m.), and Mte. Greppino (811 m.) to the village of Corona in Triassic and Tertiary strata. On the east, from Corona down to the coast at Celle, the border coincides with the junction line of the cale-schists and pietre verdi of the Voltri group, along which lie the villages of Piazza, Vetriera, Gameragna, Sanda, and Ferrari.
Within this rectangular area the hills rise near the coast to 300 ‘and 400 metres altitude, including Madonna degli Angeli immediately north of Savona, and Madonna del Monte in the south-west corner near Zinola; then in the centre to 500 and 600 metres altitude, notably Mte. Curlo, Mte. Ciuto, Mte. Cucco, and Mte. Castellazzo; and lastly to the crest-line up to 850 metres altitude, including, besides the points already mentioned, Mte. Pra (817 m.) and Mte. Negino (703 m.). ‘The hills are intersected by numerous torrents, generally in deeply eroded ravines, running towards the coast, the principal ones being the Quiliano and Quazzola at the western end, the Letimbro with its affluents the Canova, Gea, and Lavanestra in the centre, and the Sansobbia with its tributaries the Riobasco, Piantavigna, and Montegrosso at the eastern end.
All the localities, points, and ravines mentioned are geologically important for the examination of this extremely complex area, access to which is rendered easy not only by the Savona and Turin railway traversing its central and western part in numerous tunnels and cuttings, but more especially by the roads which run from different points of the Riviera road up into the hills. Among these are the great highway from Savona to Cadibona and Altare into Piémont,
DECADE VI.—VOL. III.—NO. IX. 26
4
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404 Dr. Du Riche Preller—Contact-Zone of
the road tio Santuario and Cimavalle in the Letimbro Valley north of Savona; the Quiliano and the Madonna del Monte and Cadibona roads in the western, and those from Albissola to Ellera, to Piazza and Corona, and from Celle to Ferrari in the eastern part of the area. All these roads offer a great variety of interesting and instructive exposures.
III. Tae Crrystaruine Massir. (Fig. 1.)
Within the rectangular border-lines of the Permian, Triassic, and Tertiary sedimentary formations, the crystalline massif occupies practically the whole area, with two exceptions. One of these is an island of underlying Permo-Carboniferous gneissic and sericitic schist, about 7 by 4 kilometres in length and width, which stretches from Savona and Madonna degli Angeli north-west to Santuario (98 m.). It has obviously been eroded by the Letimbro and Lavanestra torrents which join a few kilometres above Savona and discharge into the sea at that town. The other exception is a wedge of overlying Permian schist, Triassic limestone, eale-schist with pietre verdi, and Oligocene conglomerate which projects from the north near Monte Ormé and Palazzo Doria to within a kilometre of the Permo-Carboniferous island at its upper or Santuario end. The intervening gap thus forms the superficial connecting link between the two fairly equal parts of the crystalline massif. The only other island in the latter is that of Cadibonain the north-western part of the area composed of overlying Oligocene conglomerates and _ breccia, at whose eastern extremity occurs at Cima di Prato, west of Cimavalle, an extraordinary isolated outcrop of Permo-Carboniferous schist, mica-schist and gneiss; and Permian schists, surmounted by a cap of Triassic dolomitic limestone.’
The anomalous phenomenon which chiefly governs the problem of the Savona region is that the Permo-Carboniferous schists in the south, and more especially those of the Savona and Santuario island, crop out below the crystalline massif, while the Permian and Triassic strata in the north overlie it. The gneissic rocks which occupy the greater part of the southern area are crossed by two bands of amphibolic rocks 8. W. to N.E., intimately associated with the gneiss. The whole northern part of the massif, on the other hand, is composed of granitic rocks, which, in the eastern part, are surrounded on the north by a band of Permian schist, and on the south are in contact with gneiss and amphibolic rocks; in the western part the granitic rocks have the same contact as on the south, while on the west the adjacent formations are Permo-Carboniferous schists and Oligocene conglomerates. Granitic rocks also occur among the gneisses and amphibolites, and form a considerable separate mass near Madonna del Monte, in the south-west corner of the area.
IV. Tue Crystattine Rocks, The granite when fresh and unaltered resembles in some respects the Alpine type, is often porphyroid and granulitic in structure, of 1 This outcrop was pointed out by G. Rovereto in a memoir to be quoted
later. The small dolomitic cap is obviously in connexion with the larger deposits further north-east.
the Alps and Apennines in Liguria. 405
pale colour, and exhibits as its principal constituents abundant large and medium-sized elements of quartz, plagioclase, considerably or wholly kaolinized, with some orthoclase and subordinate black biotite and muscovite. Ina small isolated mass in the north near Pian di Burré, about 500 metres altitude, it is more fine-grained and in part microgranitic. The granitic rocks, both in their fresh, unaltered, and in their far more often altered and friable condition, are well exposed along the Savona and Turin railway in the Upper Letimbro Valley, in the ravines of the tributary torrents Canova and Porcheria, and in Monte Porcheria in the western part of the area. In the eastern part interesting outcrops occur on the eastern flank of Monte Negino, in the Piantavigna and Montegrosso ravines, and notably in the Sansobbia Valley near Ellera, in Monte Ciri, between the Sansobbia and Rubiasco Valleys, and in the latter valley between Piazza and Vetriera along the road from Albissola to Stella. ,
The gneiss when unaltered is rich in dark brown or black biotite with muscovite, and exhibits large orthoclase and plagioclase elements together with granular quartz. It differs from the Permo- Carboniferous gneiss chiefly in that the latter is more fine-grained, with more muscovite, and paler in colour; but the differentiation is often very difficult.1 Interesting outcrops of gneiss with associated minute gneiss and mica-schist are those along the coast between Albissola and Savona, where the gneiss is perhaps more unaltered than in other parts of the area; along the Savona and Altare road, in the Lavanestra Valley, where gneisses, amphibolites, and granite alternate; also on the road from Celle to Ferrari and Sanda, on the eastern margin of the area, where the gneiss is in contact with calc- -schist and pietre verdi, and in the south-west in the Quazzola Valley and on Monte Ciuto.
The amphibolites are largely derived from pyroxenic rocks with uralitized augite and saussuritized felspar, so much so that often hardly, if any, trace is left of the original constituents. They «re closely associated with the gneissic rocks, and differ from the pietre verdi of the cale-schist horizon on the northern and eastern border as much as the corresponding rocks of the Piémontese Alps. Of the two bands which cross the gneissic masses from south-west to north-east the larger one may be traced from the Quazzola Valley to a point where it traverses the road between Monte Ciuto and Cadibona, and then the Savona and Altare road near Monte Moro in the Lavanestra Valley; thence, on the eastern side of the Santuario island to Bric dell’ Amore, Monte Cucco, and the Albissola and Ellera road in the Sansobbia Valley. The lesser, more southern band, in contact with the granitic mass of the Madonna del Monte, crosses the road from the latter point to Cadibona south of Monte Ciuto. Some of the best exposures of the principal band occur on the ridge from Savona north to Crocetta, and towards Monte Negino, where the amphibolic banks, notably in Monte Pasasco and north of Monte Cucco, reach a thickness of over 400 metres.
1 The Permo-Carboniferous gneiss is largely developed in the Quiliano and Roviasea Valleys, in the Bormida Valley west of Altare, and further north-west down to Ferrania di Mare in the same valley; also along the Lavanestra Valley in the Savona and Santuario island.
406 Dr. Du Riche Preller—Contact-Zone of
Between the granitic, gneissic, and amphibolic rocks as the principal constituents of the massif, there are countless passages; all the rocks with rare exceptions exhibit more or less marked evidence of alteration, crushing, and lamination, and intense, often vertical folding, in striking unconformity with the subjacent Permo-Carboniferous and the overlying younger sedimentary formations.
The sedimentary formations comprise, in ascending order, the Permo - Carboniferous gneisses, mica-schists, and the dark, dull sericitic, often green chloritic schists known as phyllades or schisti plumbei; the paler Permo-Triassic sericitic schists, quartzites, and clastic Verrucano, including also the lustrous and varicoloured grey, green, and violet schisti rasatv}; and the Triassic dolomitic and fossiliferous, tegular micaceous, and black limestones, the latter corresponding to the grezzoni of the Apuan Alps and belonging to the Middle Trias. These are overlain by the Upper Trias cale-schists with pietre verdi. The extensive deposits of Oligocene fossiliferous conglomerates and breccia on the crest-line and on the flanks of the hills below that line are an important factor as evidence of a marine formation on the former, subsequently raised littoral.
V. Tae Prosiem or Acer, Srructurz, AND ORIGIN.
This problem has been fruitful of various, often directly opposed interpretations ever since 1841. Sismonda and Pareto regarded the erystalline rocks as primitive and protogine; Gastaldi classed them, including the apenninites, so called by him, as Upper Archean, though more recent than his calc-mica schist and pietre verdi zone. Zaccagna,*and with him Issel and Mazzuoli,*? in 1887 included the whole crystalline Savona series in the Permo-Carboniferous and Permian horizon of the adjoining Maritime Alps, while De Stefani,‘ in the same year, maintained Gastaldi’s view of the Pre-Paleozoic uniformity of all the crystalline rocks of the Western Alps and Liguria.
Since then the most important investigations of the Savona region have been those of Franchi (1893), Rovereto (1895 and 1909), and Termier and Boussac (1911-13), followed by the dissentient views of De Stefani (1913), who confirms his previous ones already mentioned, and considers the Savona massif formed in situ.
i Franchi, in a valuable memoir,® vindicating Pareto’s protoginic view, recognized the gneissic, amphibolie, and. granitic masses as constituting a crystalline massif older than the Permo-Carboniferous
1 Rovereto assigns these varicoloured schisti rasati to the Middle Trias, but they are, as Termier and Boussac also point out, really Upper Permian.
aD Zpecngna, ** Costituzioni Alpi Marittime’’: Boll. R. Com. geol., 1884, p. 167 et seq. ; “‘ Geologia Alpi Occid.’’: ibid., 1887, p. 346 et seq.
SAY. ssel, ity Mazzuoli, & D. Zaccagna, Carta geol. Riviere Ligure, 1887 and 1890.
4 ©. De Stefani, ‘‘L’Apennino fra Colle d’Altare e la Polcevera’’: Boll. R. Com. geol., 1887, fase. 3; ‘* Zona Serpentinosa della Liguria Occid.’’: Atti R. Accad. Lincei, Roma, 1913, pp. 547, 661.
> §. Franchi, ‘‘ Nota preliminare ‘formazione gneissica e sulle roccie granitiche del Massiccio Ligure’’: Boll. R. Com. geol., 1893, p. 43 et seq. In this memoir Franchi also describes the principal rocks microscopically and gives a list of the literature 1841 to 1893.
the Alps and Apennines in Liguria. 407
and all the other formations of the district. The gneisses and amphibolites he regarded as primitive and the granite as intrusive in, and therefore more recent than, the same. The superposition of the gneiss on the Permo-Carboniferous near Quiliano in the south-west corner of the area is, in his view, due to an inverted fold (rovescia- mento), the normal sequence of gneiss and Verrucano appearing further north, near Altare. He regards the Savona crystalline massif as forming part of the inner Alpine belt of massifs from Monte Rosa to the Grajan, Eastern Cottian, and Maritime Alps, and the Savona eneisses as akin to those of Gran Paradiso and La Levanna (Grajan Alps) rather than to those of Mont Blanc.
2. Under a novel aspect the problem was presented in an important memoir with maps and sections by Rovereto in 1909.’ His pains- taking survey of both the crystalline and sedimentary formations of the area led him to the conclusion that the reversed, anomalous sequence of the gneiss and the Permo-Carboniferous series is best explained by a local and partial overthrust or displacement of gneissic and granitic rocks from the eastern to the western part of the area. This conclusion he bases on the following grounds :—
(1) That the Permo-Carboniferous island between Savona and Santuario presents all the characteristic features of a ‘window’ which discloses that formation as the substratum, here assumed to form an anticline.
(2) That in the south-western part of the massif the gneiss mass to which the Permo-Carboniferous strata are adjacent on either side rests against the latter obliquely in opposite directions, and is there- fore fan-shaped, whereas the gneiss mass north-east of the Santuario
_island is essentially isoclinal.
(3) That in that island the eastern contact line of the Permo- Carboniferous schists and the gneiss is comparatively normal and undisturbed, whilst the western contact line exhibits marked
. unconformity, contortions, and brecciation.
Hence the inference that the eastern part of the crystalline massif is a ‘‘rooted’’ and the western part a ‘‘transported”’ area, viz. a cover-sheet by displacement.? The gneisses and amphibolice rocks of the massif are, according to Rovereto, Pre-Carboniferous, and the granite erupted in the Upper Paleozoic.*
38. A much bolder and sweeping interpretation of the Savona massif is that of Termier and Boussac in their brilliant memoir of
1 G. Rovereto, ‘‘ Zona dei Ricoprimenti del Savonese’’: Boll. Soc. geol. It., 1909, p. 389 et seq. This memoir was preceded by two preliminary notes on the same subject in 1895.
2 This fan-structure, shown in general section Fig. 2, rests on the assumption that the adjoining Permo-Carboniferous island on the right is an anticline, not a syncline.
3 Besides this solution Rovereto adumbrates three others, which, however, he considers less tangible: the first assumes the whole massif to be a rooted, the second a transported area, and the third assumes not only the Savona area but the whole of the Apennines to be a series of transported cover-sheets.
4 Franchi (op. cit., p. 64) refers to the granite as being on the eastern border intrusive also in the cale-schists and pietre verdi; these being Mesozoic, the granite would be much younger than Upper Paleozoic.
408 Dr. Du Riche Preller—Contact-Zone of
1912.! Discarding Rovereto’s local and partial ovérthrust as too timid, incomplete, and wanting in precision, they argue with characteristic entrain and incisive style and treatment in favour of a comprehensive overthrust of exotic, long distance origin, and from that point of view the subject is worked out so thoroughly that it will be interesting to outline its salient points. ©
(1) The extensive examination of the area by the authors leads them to extol the Savona crystalline massif as an ideal ‘ cover-sheet’ region, which, in point of transport and overthrust phenomena, they consider the most typical, unique, and classic of its kind in Europe. All along the roads, in the ravines, and on the heights they find in the abundant examples of intense crushing, lamination, brecciation, and friability of the crystalline masses conclusive evidence that these masses were, by subterraneous transport from an exotic source, wedged between the two sedimentary—the Permo-Carboniferous and the Triassic—formations of the Savona Hills, and thus became the dividing and contact-zone between the Alps and the Apennines.
(2) While wholly adopting Rovereto’s view of the Savona and Santuario Permo-Carboniferous ‘window’, the authors dissent from his lithological distribution of the crystalline rocks, and regard the massif as in the main composed of granitic and only to a very minor extent of gneissic and amphibolic rocks, the proportion of the three being, according to their estimate, respectively 2, 4, and %.?_ In this estimate they also include a good deal of Permian schist which they regard as altered granitic rock. Of the enormously predominant granitic masses, as also of the gneisses and amphibolic rocks, only a small part is intact and unaltered ; the great bulk is altered, structurally and mineralogically, to. mylonites, viz. bruised, crushed, laminated, mashed, and brecciated by friction of transport and by dynamic pressure.
(3) The granite when fresh contains 68 per cent of silica and in chemical composition comes near to that of Mont Blanc, but nearer to that of Elba, where Termier already previously claimed extensive granite areas as mylonites,® which he correlates with and quotes in support of the phenomena in the Savona region. Of the mylonitic granite the authors enumerate seven varieties or stages between fresh unaltered granite and the most advanced mylonitic rock as the other extreme. The first four stages comprise the fissured and brecciform, the partially crushed and laminated, the intensely laminated, and the incompletely crushed but not laminated rocks,
1 P. Termier & I. Boussac, ‘‘Le Massif Crystallin Ligure’’: Bull. Soe. géol. France, 1912, p. 272 et seq., with map and 2 sections, preceded by two ~ preliminary notes of 1911.
2 Rovereto’s distribution of granite, gneiss, and amphibolites may be estimated from his map as 3%, 7%, and jy respectively, his granite area being less than half that of Termier & Boussac.
3 P. Termier, ‘‘ Tectonique de l’Ile d’Elbe’’: Bull. Soc. géol. France, 1910, p- 314 et seq. The conclusions of this memoir were contested by B. Lotti, ‘‘ Tipotesi del Termier sulla tettonica Isola d’Elba,’’ Boll. R. Com. geol., 1910, p. 284 et seq. ; and by V. Novarese, ‘‘ I] presunto piano mylonitico del- V’Isola d’Elba,’’ ibid., 1910, p. 292 et seq.
the Alps and Apennines in Liguria. 409
while the last three represent the most advanced types of myloniti- zation, the rocks being reduced to a trachytic, phonolitic, and, as the last stage, to a talcose aspect, completely mashed and laminated, no minerals being microscopically recognizable. These rocks occur more especially along the friction surfaces of the massif. The seven varieties may be studied along the roads leading from the coast into the hills, and notably along the paths leading from Savona up to Monte Negino in the central part of the area.
4. The cataclastic structure and chaotic condition of the crystalline rocks are, in the author’s view, dominant features in favour of the massif being an overthrust em bloc. The striking unconformity, often at right angles, between the massif and the underlying and overlying formations, and its wedge-like form, thinning out from 1,000 metres in thickness in the centre to 200 metres at its north- western end, viz. in the direction of thrust, afford evidence not of a merely local and partial displacement but of the exotic origin of the entire massif.
5. The upper transport and friction surface of the massif is, in the author’s view, evidenced by the extremely disturbed and brecciated condition of the overlying younger formations in contact with the crystalline rocks. While the upper surface thus forced itself below those formations, the lower surface glided, like a traineau écraseur, along the gently undulating surface of the ‘ fixed’ Permo-Carboniferous substratum. Thus the Savona massif was, in the author’s view, transported subterraneously, in a fucte prodigieuse (sic) from the east, its rooted origin being, in common with the granite massifs of Kastern Corsica and Elba, in the Dinarides.!
The two parallel sections south to north, Figs. 2 and 3, illustrate respectively Rovereto’s and Termier & Boussac’s overthrust inter- pretations; Fig. 4 represents an alternative interpretation explained at the end of this paper. The sketch-map, Fig. 1, gives, in dotted lines, the approximate zonal direction and distribution of the crystalline rocks; but the countless passages of the three principal rocks preclude any clear definition of limits.
VI. Conctusion.
Without in the least disparaging the overthrust theory per se, which in specific cases offers the only tangible explanation of stratigraphical anomalies, it may, in my opinion, be safely averred that as regards the Savona massif, all the individual and collective phenomena so ably marshalled by Rovereto and Termier & Boussac lend themselves with equal, perhaps greater force to a more natural and rational interpretation. .
The Savona region, whose crest-line at Mte. Castlas, Mte. S. Giorgio, and Mte. Greppino lies at about 825 metres altitude, forms a depression between Mte. Settepani (1,391 m.) in the Maritime Alps on the west
1 The theory of the Dinarides being the rooted origin of the three granitic areas is founded on G. Steinmann’s often-quoted memoir, ‘‘ Alpen und Apennin,’’ Monatsber. Deutsche Geol. Ges., 1907, p. 177 et seq.; his ‘‘dinaric coyer-sheets ’’, however, are assumed to have been transported, not direct from east to west, but circuitously along the curve-line of the Alps.
410 Dr. Preller—Contact-Zone of Alps and Apennines.
and Mte. Ermetta (1,267 m.) in the Voltri Apennines on the east. - The depression of 500 metres thus constitutes a syncline, in the centre of which the region is deeply cut from north to south, and in its lower part, between Santuario and Savona, is eroded to a width of 4 kilometres by the Letimbro and Lavanestra. In striking contrast to the regularly stratified and undisturbed slopes on the north or Po side of the Apennines, the Savona region is intensely folded, contorted, and faulted, the maximum of disturbance being in the centre, viz. in and near the Letimbro Valley immediately west and north of Santuario, where all the rock formations converge.
_ As previously mentioned, the northern part of the region is largely covered, in places to a depth of 400 metres, by Oligocene marine conglomerates and breccia which represent a former littoral formation raised in later Oligocene or early Miocene times. It was during that emergence and raising from the sea that the Savona region was, by enormous pressure from below and from both sides west and east, compressed, folded, fractured, brecciated, and, as Termier and Boussac term it, reduced to a chaotic condition, a process repeated on a smaller scale in Post-Pliocene times and followed in each case by a settling which gradually produced the present depression and contact-zone between the Alps and the Apennines.’
This enormous compression by repeated earth-movements explains the crushing, lamination, brecciation, and more or less intense alteration of the crystalline rocks, as well as the highly angular unconformity between them and the sedimentary formations, and the marked disturbance of the latter along the lines of contact. The many passages and stages of alteration in the crystalline rocks render a differentiation between transformed granite, gneiss, and amphibolite very difficult; but the granitic rocks being largely predominant and of eruptive origin, it is by no means improbable that the gneissic and amphibolie rocks too are derived from granite which thus constituted the whole original massif.? Its eruption and spreading out over the Permo-Carboniferous formation must in that case have taken place about the Middle Permian period, as the Upper Permian or Verrucano in part overlies the massif. This interpretation thus solves without an overthrust the cardinal problem of the abnormal superposition of the crystalline rocks on the Permo-Carboniferous formation.’
If, on the other hand, the problem is to be solved by an overthrust, it appears more probable that the whole crystalline massif was
1 7,. Mazzuoli, in an interesting memoir on the ‘‘ Formazione dei Con- glomerati Miocenici nell’Apennino Ligure ’’, Boll. R. Com. geol., 1888, p. 9 et seq., mentions the noteworthy fact that soundings carried out by the Italian Marine Department along the Riviera littoral of Genoa and Savona have proved the existence of submarine river valleys at depths up to 900 metres at 4 nautical miles from the shore. The ratio of fall below sea-level is thus about the same as that from the Apennine crest-line to the coast.
= The gneissic rocks of Valdana, in the south-eastern part of Elba, are by common consent of granitic origin, though older than the microgranites in the
west of Elba (B. Lotti, op. cit., p. 285). 3 By this interpretation Termier and Boussac’s exotic granite mass, section
Fig. 3, whose submarine part is of course purely hypothetical, becomes simply an ordinary intrusive tongue formed in situ.
A. R. Horwood—Upper Trias, Lewestershire. 411
transported, not from the east, but from a much nearer root in the west, that is, from the Argentera gneiss and granite massif in the Maritime Alps, whence it ‘glided’ over the intervening Permo- Carboniferous formation of the Montgioie range to its present position probably in Mid-Permian times.!. The overlying Verrucano, Triassic limestones, and calc-schists with pietre verdi were, in that case, similarly transported from the Montgioie range at a later, probably in the Eocene period, the calc-schists being pushed beyond the Savona massif as a cover-sheet forming the present abnormally located Voltri group.” This alternative overthrust is indicated in the section Fig. 4.
The interpretation as an overthrust is alluring, but of necessity hypothetical. It has been truly remarked that there is no difficulty, obstacle, or objection which the overthrust theory cannot overcome by geometrical designs.* Rovereto himself calls it geopoetismo.* When, therefore, a stratigraphical problem admits of a more tangible and legitimate in situ explanation, the presumption and balance should logically be in favour of the latter, and this may reasonably apply to a region geologically so singular and attractive as that of the contact-zone of Savona.
1V.—Tuer Upper Trtas oF LEICESTERSHIRE. (Continued from the August Number, p. 371.) By A. R. Horwoop, F.L.S. (PLATE XVII.) 7. PaLmonroLoey.
7] \HIS district is of especial interest from the paleontological point of
view in that the different members of the Upper Trias each afford a representative though not extensive flora and fauna. The scantiness of the material, in so far as the Lower Keuper and in some respects the Dane Hill Series are concerned, is due rather to the absence of good sections. ‘This cannot, however, be said of the Rhetic beds, for the section at Glen Parva is one of the finest in the Midlands.
Lower Keuper Sandstones and Marls.
Plant-remains.—In the higher part of the waterstones at Appleby, in the marls intercalated with sandstones, obscure plant-remains, possibly Equisetacez, occur.
Annelid or Crustacean tracks.—At Kegworth the surfaces of the sandstones are covered here and there with obscure trails or tracks which may be organic.
Footprints of Cheirotherium.—A footprint, discovered about 1879 -by Mr. T. Large, was found at Kegworth in waterstones, which must
1 The Permo-Carboniferous ‘ window’ would in that case be a syncline, and the adjacent crystalline mass west would be, not fan-shaped, but isoclinal.
2 Termier and Boussac themselves assume the younger formations to have moved as cover-sheets from west to east, viz. in the opposite direction of the crystalline massif.
* V. Novarese, ‘‘ Il Profilo della Grivola, Alpi Graje’’: Bull. R. Com. geol., 1909, p. 497 et seq.
+ Op. cit., p. 408.
412 <A. R. Horwood—Upper Trias, Leicestershire.
be not far from the green beds at the base. It is described and figured in the Appendix (see infra, pp. 421-2, Pl. XVII, Fig. 2).
Rhynchosauroid footprints.—Some obscure footprints resembled this type at Kegworth, but are too indefinite to identify with any certainty. In the Building Stones on the opposite side of the River Trent, at Weston Cliff, footprints ascribed to Cheirotherium were found years ago. Others were discovered in similar beds at Brizlincote. In the waterstones near Barton, on the Ashby Road, near Mr. Wardle’s house, footprints of Chetrothertum are also recorded by Molyneux and Sir Oswald Mosley at Barton Bridge.!
In the green beds lying over the basal conglomerate at Colwick, Notts, Wilson found guwisetites columnaris, and scales of fishes, Semtonotus sp., and of a paleoniscid type. In the same beds, in the Midland Railway cutting, the Rev. Dr. A. Irving found footprints of a Labyrinthodont.
The officers of the Survey have found obscure remains of plants during their work in the same district. They found annelid tracks at Westhorpe, Dumble, near Southwell, and suggest the possibility of fossils in rocks at Markham Clinton. In the green beds they found obscure remains of plants, and at Farnsfield plants showing cell structure and bits of plants and ill-preserved fish-scales at Boughton Dike.
Upper Keuper Red Marls and Sandstones.
In the Orton-on-the-Hill Sandstone Group so far no plants have been discovered. In the Dane Hill Sandstone Group at Leicester, however, a number of fossils have been found. They were described at an ‘early date by J. Plant, 1849 (Brit. Assoc. Report, 1850), and more fully by his brother, James Plant, in 1856.
Alge(?).—Some carbonaceous bands, intercalated between sand- stones, were said by Plant to be due to Alge. Certain casts of obscure plant-like structure may be referable to Algz, but they are not satisfactory enough to place the matter beyond doubt. Well- boring, Leicester.
Equisetites arenaceus.—Certain casts of Equisetaceous plants which are characterized by long internodes and nodes with well-marked furrows may be referred with some reason to the above. There is no resemblance between them and Schizonewra, to which certain pith- casts in the Lower Keuper of Bromsgrove are referred by Mr. Wills. Shoulder of Mutton Hill Cutting, Westcotes.
Schizoneura sp.—Dane Hills.
Stigmarites. — A Lycopodiaceous rootlet may be provisionally referred to this genus, though it presents no characters for defining a separate species. Dane Hills. .
Voltzia heterophylla.—Specimens found by Plant are referred to Voltzia, and in the British Museum a specimen (B.M. 24190) is referred by Professor Seward to the genus, though named Gorgonia Keupert. A cast of the stem is probably referable to this species, and
1 Coleman refers to these and says that Estheria minuta oceurs in water- stones or white beds.
A. R. Horwood—Upper Trias, Leicestershire. 413
another may be the male cones, labelled Hcehinostachys oblongus. Dane Hills, Shoulder of Mutton Hill, Leicester.
Incerte sedis —A number of other specimens may be doubtfully regarded as plant-remains, some associated with supposed fucoid, or Gorgonia, or annelid tracks, or as Lehinostachys oblongus. In the carbonaceous bands are obscure plant impressions resembling the leaves of Pterophyllum.
Annelid or Crustacean tracks. —On the surfaces of the green gritty beds, below the Acrodus bed (Annelid bed), are numerous tracks and trails which may be regarded as the work of Annelids or Crustacea. Their mode of occurrence rather than their actual form suggests this, though it is analogous to that of other fossil tracks usually ascribed to Annelids. Well-boring, Shoulder of Mutton Hill, Dane Hills. They occur also in the Acrodus beds and Estheria marls..
Estheria minuta (Alberti).— Whilst this little bivalved Phyllopod is perhaps most common in the marls above the Acrodus sandstones, it occurs throughout the series, and thus ranges from the waterstones to the Rheetic beds. It is often numerous in calcareous marl partings, whilst in the sandstones it is rare. Belgrave, well-boring near west bridge, Shoulder of Mutton Hill, Dane Hills, Aylestone Road.
Acrodus keuperinus (M. & S.).—Dorsal fin-spines of this species are not uncommon in the Acrodus beds, and less so in the Annelid beds below, which are the equivalent of Brodie’s green gritty marls (Q.J.G.8., 1893, p. 174). Teeth are also to be found in the Acrodus beds. Shoulder of Mutton Hill cutting, Dane Hills, Aylestone Road.
Acrodus minimus, Ag.—A dorsal fin-spine found by Browne at Shoulder of Mutton Hill is assigned to Hybodus minor, which is in part, according to Dr. A. 8. Woodward, to be referred to this species.
Acrodus sp.—Others may be assigned to this genus provisionally from Dane Hills and Aylestone Road, whilst many ichthyodorulites, _ fish-teeth, and spines may be similarly ascribed to this genus. The
coprolites and fish-scales from Leicester, Dane Hills, and Aylestone Road are of more doubtful affinity.
Gyrolepis quenstedti (Dames).—Browne found scales referred to this species at Aylestone Road in the Annelid bed.
Colobodus frequens (Dames).—See the last.
Labyrinthodontia.—A footprint or ‘footstep’, ‘‘4 inches in diameter, in form similar to the well-known Labyrinthodont footmarks of Storeton in Cheshire,’”’ was found by Plant in the Annelid beds in the railway cutting at Shoulder of Mutton Hill, and a footmark in the same beds at a well-boring near the west bridge. Plant also found fragments of bone 2 inches thick, 5 inches long, and 1 inch in diameter in the Annelid bed in the cutting, and Browne found others which he ascribes to an amphibian at Aylestone Road. This is interesting as Brodie also found Labyrinthodont bones in the Green Gritty Marls at Shrewley. Plant records them also for the Roman wall boring.
Reptilian remains.—Possibly some of the foregoing should rather come under this head. A fragment of a tooth from Bede House Meadows is certainly reptilian. he fossil referred to, Zanystropheus, Owen, was half a caudal vertebra according to Professor H. G. Seeley,
414 A. R. Horwood—Upper Trias, Leicestershire.
and not referable to that genus, and later he said it came from the Rheetic. ; Red Marl.
Voltzia sp.—Mr. Harrison records the fact that the only fossil he found in the Red Marl was ‘‘ casts of the spreading leaves” of Voltzva. It is probable that careful search, as suggested by Browne, would reveal the occurrence of teeth, ete., of sharks in the skerries and coarse sandstones. The late Mr. G. Lomas found Estheria minuta var. brodieana in the Red Marl at Oxton, near Liverpool. Near Newark scales of Gyrolepis associated with salt pseudomorphs have been found in the grey beds. In some dolomitic skerries there are obscure traces of organisms which might be the casts of mollusca. In marls and clays containing pyrites or allied decomposing agents where sulphuric acid is formed fossils may be dissolved as pointed out by P. M. Duncan. The high proportion of sulphuric acid in the Gypsiferous Marls is in itself a reason for their apparently (I would emphasize this word, and endeavour to stimulate research for traces of life at this horizon, rather than discourage it, as is usually the practice) unfossiliferous nature.
Tea-green Maris.
It is due to the last cause that probably the occurrence of fossils in the T'ea-green Marls is little known. But though they are not abundant they occur in some variety. They have been found in the West of England and at other places. ;
In Leicestershire at all of the three principal exposures, Gipsy Lane, Spinney Hills, and Glen Parva, scales of fossil fish have been discovered. ‘They belong apparently to a Semionotoid type. They were especially abundant at Spinney Hills, where the Tea-green Marls were green and blue and buff in colour. With them occur Hstheria minuta (Alberti) in some quantity. There are obscure remains of what are probably plants and apparently casts of shells.
Mr. Harrison records that he found an insect wing, but he said it perished immediately, and it is more than probable that it was Estheria. At the same time the lithic structure is similar to the insect-beds of the Rheetic and Upper Lias, so that, especially as insect remains occur in the Rheetic, not far above the bone-bed, it is less improbable. At the Spinney Hills Colobodus frequens (Dames) was found and teeth and scales of a paleoniscid fish.
At Glen Parva there are, as at Gipsy Lane, regular bands of fish- scales, and, in addition to these, Orbiculovdea townshend, Davidson, and annelid tracks have been found by Mr. A. J.S. Cannon. ‘This Brachiopod is common to the Rheetic also.
The continuity of the fauna is, moreover, carried on by the occurrence of true Rheetic fossils in the Sully Beds below the Bone- bed, represented in the West of England and Wales.
Rhetie.
In the notes which follow the localities given are preceded by a number indicating the horizon at which the specimens were found, which is correlated with the Pylle Hill sequence as defined by Wilson.
id
A. R. Horwood— Upper Trias, Levcestershire. 415
The same table gives the corresponding beds (by number or letter) of the sections relating to this district as well as that of Stanton-on-the Wolds in Notts for comparison (see Table, p. 419).
Frora.—Alge.
7. Crown Hills. Too indefinite to give any generic or specific name, and possibly (as they are mere casts) something else.
Pterophylium brevipinna, Heer. Cf. Otozamites acuminatus (L. & H.). Intermediate between this and O. obtusus (L. & H.). 4. East Leake. 2. Glen Parva.
Plant-remains. Fossil wood. Fragments of stems, branchlets, leaves, possibly in some cases allied to Podozamites. 2. Kast Leake. 2. Glen Parva.
C@LENTERATA.—? Heterastrea rhetica, Tomes.
26. Spinney Hills. Harrison speaks of ‘‘oval markings with fine strie radiating from the centre”’, which may possibly be referable to this coral.
Annetipa.—Archarenicola rhetica, Horwood.
2. Glen Parva. A second specimen has been found.
Annelid remains (tracks and burrows). 2a. Spinney Hills. 7-9. Glen Parva.
Crustacea.—Estheria minuta (alberti). 3. Spinney Hills, Glen Parva. Junction of the Tea-green Marl and Rhetic, Gipsy Lane.
? Eryma. Several fragments referable to this genus. 20. Glen Parva.
Insecta.—CoLEoPrrra. Pterostichites' grandis, sp.nov. (Pl. XVII, Figs. 1a, 10.)
At 3 feet above the Bone-bed at Glen Parva Mr. A. T. S. Cannon found a single elytron of a beetle, associated with fragments of chitin of insects, along with marine shells. As it does not appear to have been hitherto noticed, the following description is given :—
Right elytron, 18 mm. long and 7 mm. broad at the widest part, oblong acute, the anterior and posterior margins subparallel for part of their length; suture following the margin regularly at a distance of less than 1 mm., striz ten, subparallel, and arising from the proximal extremity at equal distances, converging towards the anterior distal extremity, surface subconvex, coriaceous, the proximal extremity exhibiting a sinus left by the articulatory process.
I am indebted to Mr. T. R. Goddard for confirming my identification of this fossil as a right elytron of a beetle. He considers that it may belong to some form allied to Pterostichus, some species of which are marine.
Though such remains are not uncommon in the insect limestone (bed p of White Lias) they are rare in the Westbury Beds. They have been found, however, in bed 1 at Stoke Gifford by Dr. A. R. Short in the Upper Rhetic or Cotham Beds.
1 The genus Pterostichites is proposed to include fossil forms presumably related to the modern genus Pterostichus.
416 A. R. Horwood—Upper Trias, Leicestershire.
Gastrrovopa.— Cylindrites ovalis, Moore. 4. East Leake. I consider Actgonina valleti, Stoppani, recorded from here, should be called Cylindrites ovalis.
LAMELLIBRANCHIATA.—? Leda alpina, Winkler. Wigston. It is probable that MWucula variabilis, Quenst., recorded from here, is referable to this species.
Pteria contorta(Portl.). 2. Ash Spinney, Crownend Wood, Spinney Hills, Barrow-on-Soar, Barrowcliffe, Glen Parva, East Leake, Vulcan Road, Haddon Street, Moat Road, Crown Hill boring. 26-3. ‘Spinney Bile? Billesdon.
Pseudomonotis fallax, Pfliicker. 10. Glen Parva, probably from this bed. 210. Spinney Hills. Cf. Anomia schafhaulti, Winkler. 26. Glen Parva.
Pleurophorus elongatus, Moore. 1. Spinney Hills.
? Myophoria inflata, Emmerich. 26. East Leake.
Myophoria sp.. 26. Glen Parva. Cf. If. emmerichi, Winkler.
Chlamys valoniensis (Defrance). . 25. Kast Leake, Glen Parva, Spinney Hills. 2, 4. Wigston, Crown Hill boring.
Dimyodon intusstriatus, Emmerich. 25. Glen Parva (rare).
Volsella minima (Sow.). 26, 10. Glen Parva. 26. Spinney Hills.
Gervillia precursor (Quenst.). 2a, 2b. Glen Parva.
2 Gervillia ornata, Moore. 26. Glen Parva (rare).
Pleuromya sp. (but perhaps Jsodonta). A. ‘‘ cream-coloured”’ shell. 2. Culvert between Earl Howe Street and Mere Road in a flage band, about 10 feet below the surface.
Myacites striatoglanulata, Moore. 2b. Glen Parva (rare).
Astarte sp. Glen Parva (? A. swessi, Rolle).
Isocyprina ewaldi (Born.). 2. Glen Parva. 2a, 10. Spinney Hills, ‘Glen Parva. 206. Kast Leake. 4. Glen Parva. 2. Junction of Donnington Street and Mere Road. 7. Diseworth Street.
Protocardia rhetica (Merian). Cottagers Hill. 26. Spinney Hills.
26. Glen Parva. 26. Kast Leake.
Cardium cloacinum, Quenst. 2. Glen Parva (abundant). ;
Schizodus depressus (Moore). 1. Spinney Hills. 26. Glen Parva.
Anatina precursor, Quenst. 26. East Leake.
Ophiolepis damesii, Wright. (Pl. XVII, Figs. 3, 4.) 26. Spinney Hills. Harrison was the first to record this for Britain. But he states that it had been found up to 1880 (Sczence Gossip, 1880, p. 56) at Vallis, Garden Cliff, Stratford-on-Avon, Rugby (in White Lias), Aust Cliff, Penarth to Lavernock, as well as at Hildersheim.! He said he considered there were two distinct
species, and his specimens include a large and a small form. Wright
figured the small form (enlarged), but his description covers the large form. Recently Mr. Cannon brought me a number of specimens from Glen Parva, the large form (Pl. XVII, Fig. 3) from 15 inches above the bone-bed, the small form (Pl. XVII, Fig. 4) 4 feet above
1 Brodie found it at Summer Hill in Warwickshire, and says it occurs at Westbury midway between the Hstheria and upper bone beds, and that Wright places it in the Cardium Shales. Wilson found it at Pylle Hill (bed f). It was found at Glen Parva, but not in situ, some time ago.
A. R. Horwood—Upper Trias, Leicestershire. 417
the bone-bed, associated with fish. As Harrison found his specimens with fish also it is probable that this is the same bed, and the small form is no doubt referred to.
I was myself at first inclined to consider there were two species, but more material being forthcoming I came to the conclusion that the speciesis dimorphic. It may be noted that the large form appears first, the small one later. In this case the small one may be regarded as degenerate, as Mr. Cannon has suggested to me. ‘The opinion I hold is shared by Mr. W. K. Spencer, to whom they were submitted by Dr. Bather, whose advice I had sought upon this point. Dr. Bather, like myself, was inclined to consider the forms distinct, but concurs with my later view, borne out by Mr. Spencer. It is sufficient to remark, at this point, that if the large form is more specialized than the small one, the line of degeneration here is connected with a reduction in the length of the arms, and a relative increase in their width at the base, causing a corresponding decrease in the width of the interbrachial areas. Some other differences are correlated with this. But as it is proposed to publish a separate account of these forms, figures of both are merely given here to show the dimorphism of this species (see Pl. XVII, Figs. 8, 4). Wright’s description and figure being in some respects incomplete it will therefore be necessary to amend them. Since the material is not easy to study from the pyritized nature of the matrix, it is hoped further material will throw some light upon obscure points.
“* Echinus”’ (? Pseudodiadema). Browne mentions that Mr. A. EH. Baker found a fragment of an Hchinus test at Spinney Hills. _ Echinoderm ossicles. \ Barrow Hill.
Piscus.'— Hybodus cloacinus, Quenst. (teeth and dorsal fin-spines). 1. Spinney Hills. 2. Haddon Street, Crown Hills.
Hybodus minor, Ag. (teeth). 1. Spinney Hills, Glen Parva. 2. Kast Leake. These are founded on teeth, and the dorsal fin- spines termed WVemacanthus monilifer are probably referable to the same species as well as, perhaps, Sphenonchus.
Nemacanthus monilifer, Ag. (dorsal fin-spines). 1. Spinney Hills, Glen Parva. 2. East Leake.
Sphenonchus (cephalic spine). 1. Spinney Hills.
Acrodus minimus, Ag. (teeth and spines). 1. Spinney Hills. 2. Haddon Street, Glen Parva, East Leake, Barrow.
Ceratodus latissimus, Ag. (teeth). 1. Spinney Hills. 1. Glen Parva (?).
Gyrolepis albertii, Ag. (scales). 1. Spinney Hills, Glen Parva, Barrow. 2. Haddon Street, Kast Leake, Glen Parva.
Gyrolepis quenstedti, Dames (scales). 2. Hast Leake.
Colobodus maximus, Quenst. (teeth and scales). (= Sargodon tomicus, Phén.) 1. Spinney Hills.
Colobodus sp. 1. Haddon Street (scales), Glen Parva.
Sargodon sp. ?1. Barrow Hill.
1 See Dr. A. S. Woodward, Trans. Leic. Lit. and Phil. Soc., 1889, p. 18 et seqq.
DECADE VI.—VOL. III.—NO. Ix. 27
418 A. R. Horwood—Upper Trias, Leicestershire.
Saurichthys acuminatus, Ag. (teeth), Regarded by Dr. AOS Woodward as perhaps the same as Belonorhynchus. 1. Spinney Hills.
2. Haddon Street, Glen Parva.
Pholidophorus higginst, Eg. (= P. mottiana, Harrison; P. nitidus, Eg.) 26. Spinney Hills, Glen Parva, Crown Hills.
Dapedius sp. 2. Hast Leake.
Fisu-reetd, Fisu-pones. 1. Spinney Hills. Copzorrrss at Glen Parva, East Leake.
Ampurpia.—‘‘ Lozomma” (teeth, vertebra, rib bones). 1. Spinney Hills. a
Labyrinthodont remains (jaw, bones, left ramus of the mandible, teeth, etc.). 1. Spinney Hills. 2. East Leake, Glen Parva.
Reprit1a.—‘‘ Plesiosaurus rostratus”’ (teeth, bones, ribs, vertebree). 1. Spinney Hills. 24.Glen Parva. (Probably these belong, according to Dr. Watson, to another species.)
Ichthyosaurus sp. (teeth, vertebre, bones, coprolites). 1. Spinney Hills (vertebra near Moat Road).
Drvnosavria.—2. Limb-bones, East Leake. Rysosteus owent, Woodw. & Sherb. 2. East Leake. Dr. Watson considers these may belong to a Plesiosaur as yet undetermined. Incerte sedis. Saurian teeth, vertebrz, bones, coprolites, vertebre of Amphibia or Reptilia, casts of centra, concavo-convex bodies like Discina, small circular bodies like cup-corals (at Glen Parva, coprolites). 1. Spinney Hills.
Fragmentary remains of Ampuipra and Reprinia. 1. Glen Parva. Savrian Bones anp TertH. 1. Haddon Street.
The correlation of the sections I have given shows that no beds exactly comparable with the White Lias occur in Leicestershire. That the top bed (1 of Richardson) may be the Cotham Marble, however, is shown by its intermediate character, and that Pseudo-
monotis occurs in the upper part of the Compound Bed, and may be |
equivalent to the Psewdomonotis bed as Mr. Richardson suggests, but the rarity of this species makes this point inconclusive. Harrison said he found it at Spinney Hills, and correlates it with a limestone higher up, remarking that he found beds like the Guinea Bed at Crown Hills (Lower Lias).
There is evidence that the Bone-bed, though persistent, and hardly recognizable at East Leake, is a very attenuated type of the West of England equivalent, whilst there were two at Stanton, as elsewhere.
The similarity of fossils at the points named proves the fauna to be, as a whole, uniform. The unfossiliferous character of the Upper Rhetic and anomalous juxtaposition of intermediate beds at the top under beds with Ammonites planorbis, Ostrea liassica, and Lima gigantea, and so close to the Upper Rheetic, as pointed out by Mr. Richardson, in conjunction with gaps between the Tea-green Marls and the Bone-bed, shows that there were locally as elsewhere two periods of alteration of level and conditions.
|
419
A. hk. Horwood—Upper Trias, Leicestershire.
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The disputed point as to whether Hstheria occurs in the limestone at Glen Parva is somewhat simplified by the fact that Harrison found it at Spinney Hills in the bed in question, and Wilson found Estherta in drift derived from these nodular limestones at Stanton-on-the- Wolds.
The outliers of Rhetic beds at Needwood exhibit very peculiar variation. Below what may be regarded as the Avicula contorta zone, without a bone-bed, come, in two cases (at Brakenhurst Hill and Butter- milk Hill), 100feet of white marl with bands of marl limestone overlying red and blue conchoidal Keuper Marls. These white beds must be the Tea-green Marls' (proved in the same latitude between Melton and Newark), which have attained an extraordinary development. In the former case the Rhetics are 38 feet, in the latter 24 ft. 7in. thick, the bulk of which appears to belong to the Lower Rhetic or Westbury Beds. Moreover, at Swilcar Lawn Oak 38 feet of black shales were pierced in a well-sinking. It is thus clear that the northern development of the Rheetics, whilst exhibiting some uniformity in the fauna, is characterized by the absence of beds represented elsewhere to the south, and the greater development of some other beds, pointing to considerable diversity of physical conditions, a fact also demonstrated by the character of the flora and fauna and the state in which it is preserved.
In regard to the White Lias the rather anomalous beds at Glen Parva owe their characteristics to the fact that north of Warwickshire (taking Rugby as an example) the White Lias begins to die out. There would seem, then, to be two different centres of deposition or regions: (1) from Leicestershire to Yorkshire, where more marine conditions prevailed, and (2) Warwickshire to Somersetshire, where estuarine conditions were also prevalent. Probably the southern flora and fauna were derived from the northern, which in turn were derived from the eastern European region. As pointed out by Mr. Richardson, this is, no doubt, due to the fact that the British Rhetic phase is later than the Continental, and no doubt the North British was earlier than the Southern phase, accounting also for the discontinuity of Sully Beds and White Lias.
EXPLANATION OF PLATE XVII.
Fie. 1.—Insecta (Coleoptera). 1la.—Right elytron of a beetle, Pterostichites grandis, sp. noy. A.R.H. 1b.—The same restored. From 3 feet above the bone-bed, Lower Lias, Glen Parva, associated with fragments of chitin of insects along with marine shells (see Fig. 1a).
Fic. 2.—Natural cast of Chirosauroid footprint (left pes?), form ‘‘KP”’ (Beasley), (reduced). From the Keuper of Kegworth, Leicestershire. Fics, 3, 4.—Ophiolepis damesti, Wright. Lower Lias: Glen Parva. Fig. 3,
the large form (nat. size). Fig. 4, the small form (enlarged).
1 It is unlikely that they are the Sully Beds in part—missing in Leicestershire and elsewhere.
(To be continued.)
q > a 4 f
R ‘ a
—— sO
a
Gor. Maa., 1916. Pirate XVII.
d. J. 8. Cannon, photo.
FOSSILS FROM LEICESTERSHIRE.
F. T. Maidwell—The Kegworth Footprint. 421
VY.—Norr on tHE KerewortH Footprint. By F. T. MAIDWELL. . (See Pl. XVII, Fig. 2.)
(V\HIS footprint was noticed by Mr. A. R. Horwood in the British
Association Trias Committee’s Report for 1909 (5) and there referred to as resembling Cheirotherium herculis (Kg.) and to be from the Lower Keuper Sandstone. As mentioned in that note, it was found in an excavation at Kegworth, North Leicestershire, some thirty-four years ago by Mr. J. Large, who in 1909 presented it to the Leicester Corporation Museum. It is interesting as being the only Chirosauroid print so far recorded from the Keuper rocks of _ Leicestershire, and proves the occurrence in that area of animals and conditions similar to those which existed in Cheshire, Staffordshire, and Warwickshire during the Keuper period.
The print shows the cast of an impression of four digits with no trace of a fifth. Close behind the first digit the surface is slightly raised and protuberant, but so little that it needs no further notice. The first digit has its origin farther back than the roots of the other toes and is the shortest of the four, the third being the longest. The angle of divergence between the first and second digits is considerably greater than between either the second and third or the third and fourth. The outer edge of the third digit has an inward curve, whilst the fourth is distinctly curved towards the third. Unfortu- nately a portion of the distal end of the fourth digit has been broken off on its inner side. The digits taper rapidly from their root ends, and in cross-section are slightly rounded on the sides with a slight flattening of the soles. The digits show no trace of pads, but their root ends stand out slightly from the posterior under surface. Short folds can be detected crossing the inner sides of the second and third toes. The digits were deeply impressed towards their distal ends, the greatest depth shown on the cast being about 4 centimetres.
The following are the principal dimensions :—
Length from distal end of 3rd digit to the broken posterior end, 12°5 cm.
Greatest breadth between the distal ends of Ist and 4th digits, 15,cm.
Distance between centres of root ends of digits I and IV, 7°5 cm.
Distance between centres of distal ends: I to II, 6°5 cm.; II to IH, 6 cm. ; III to IV, 6 cm.
I. II. Iii. IV. Length of digits . : : ; 25 4 5°5 4°7 cm. Breadth of digits : j 4 3°3 5 5 4°5 em.
[All measurements are given in centimetres. |
In describing a fossil footprint it is always necessary to remember that we are dealing with the impression, or cast of an impression, of a foot and not with the foot itself. The same foot may in the course of a few strides make many different impressions, due mainly to the ‘varying condition of the mud upon which the animal walked.
This footprint probably represents the left pes, but as it is a solitary specimen we cannot say definitely whether it be pes or manus, but
1 Being Appendix (11) to Mr. A. R. Horwood’s paper on the Upper Trias of Leicestershire.
422 F. T. Maidwell—The Kegworth Footprint.
the foot which made it was evidently digitigrade. The footprint from Kegworth is not Chirosaurus hereulis (2).
This footprint bears some resemblance to the two groups of Chirosauroid prints which Mr. H. C. Beasiey has classified as Group K (1, 8) and Group P(4). It resembles the prints of Group K in general outline and two of its digits are curved and also longer
Fic. 1.—The Kegworth Footprint. a, Outline of footprint; the dotted line indicates the broken posterior end (4 nat. size). 6, longitudinal section of digit III. c, cross-section of same digit. See also Pl. XVII, Fig. 2. F, T. Maidwell del.
than wide, but it differs from that group as the digits are not triangular in section, and two of them are neither greater in length than the width at the roots nor are they curved. It resembles those of Group P in that there is evidence of the posterior end gradually merging into the surface of the stone and also in the comparatively short, quickly tapering digits; but it differs from that group in that neither the two outer toes are equal nor are the two inner, and the two digits III and IV curve inwards.
It may be that the prints of these two groups were made by aborted forms of some of the feet which made the five-toed prints in Mr. Beasley’s Group A, but at present this is only surmise. So for the present it is advisable to separate these four-toed prints in a group or groups apart, and as this Kegworth print is intermediate in character between the Groups K and P, I propose to label it Chirosauroid footprint, Form KP (Beasley), from the Keuper of Kegworth, Leicestershire.
REFERENCES. 1. H. C. BEASLEY. 1898. ‘‘Notes on Examples of Footprints from the Trias in some Provincial Museums ’’: Proc. Liver. Geol. Soc., vol. viii,
p. 233, pl. xi, fig. 5.
—— 1901. ‘‘Notes on Type Specimen of Cheirotheriwm herculis (Egerton) ’’: Proc. Liver. Geol. Soc., vol. ix, p. 81, pl. v.
to
3: 1902. ‘‘On two Footprints from the Lower Keuper, and their relation to Cheirotheriwm storetonense’’: Proc. Liver. Geol. Soc., vol. ix, p. 238.
4, 1909. ‘‘Seventh Report of the Committee for the Investigation of
the Fauna and Flora of the Trias of the British Isles. Report on
Footprints from the Trias.’’ Part vi. Rep. Brit. Assoc. (Winnipeg),
1909, pp. 151-2, with fig.
5. A.R. HoRwoop. ‘‘ Preliminary Notice of the Occurrence of Footprints in the Lower Keuper Sandstone of Leicestershire’’: Rep. Brit. Assoc., 1909, p. 162.
.
i
Reviews—Geology of Whitby and Scarborough. 423
REVIEWS.
———._—
I.—Tur Gronosy or rue Country serween Wuirsy anp Scar- BoroueH. Second edition. Memoirs of the Geological Survey, 1915. 8vo; pp.iv+144. London: E. Stanford, Long Acre.
(J\HE second edition of this memoir has been prepared to accompany
the new colour-printed map of the district ; it has been brought up to date and considerably enlarged, two of the new features being chapters on the paleontological classification of the local Jurassic rocks by Mr. S. S. Buckman and on the fossil plants of the Lower Oolites. The scope of the memoir has also been slightly enlarged by the inclusion of a small triangular area around the town of Whitby, hitherto comprised in the Cleveland memoir.
The geology of this district possesses many features of interest and ‘includes problems which cannot yet be regarded as solved. Two questions, however, stand out before all others in importance, namely, (a) the origin and stratigraphical relations of the Blea Wyke beds and (6) the glacial phenomena of the district.
With regard to the Blea Wyke beds, recent work by Mr. Buckman, Mr. L. Richardson, and others has shown that the thickness of the strata found at Blea Wyke, but absent elsewhere in North-East Yorkshire, is even greater than was formerly supposed, amounting perhaps to as much as 200 feet. According to the zonal evidence there is probably a non-sequence below the Werinea bed, which is regarded as the base of the Aalenian, while the Blea Wyke beds proper and Sétriatulus shales are Yeovilian. As is well known, elsewhere the base of the Dogger rests directly on the Upper Lias (Whitbian), the Yeovilian being absent. . With regard to the suggestion that the presence of these strata at Blea Wyke only is due to the shelter afforded by the existence at that time of a submarine fault-scarp at Peak, the treatment in this memoir is not satisfactory. The sections devoted to the discussion of this point read like a mosaic of two statements written from opposite points of view. On p. 82 we read, “‘the suggestion . . . involves many impracticable suppositions. Moreover, the facts to be explained do not arise from the thickening of beds, but from the presence of additional beds not found elsewhere in the neighbourhood.”’ The latter sentence shows a total misunder- standing of the ideas of Mr. Hudleston and others. The supposition of the inter-Jurassic age of the Peak fault was put forward to explain precisely this point, namely, the presence of additional beds, and had nothing to do with variations in the thickness of beds which exist elsewhere. However, at the bottom of the same page the writer of the memoir goes on to accept wholeheartedly the theory which he has just stated to be impracticable. It is shown that in Jurassic times there must have been a fault somewhat along the line of the Peak fault, with a throw of 200 feet. This is a higher figure than was claimed by earlier writers.
Mr. Buckman’s work on the Ammonite zones has revealed many points of interest in the correlation of the various members of the Jurassic rocks above the Dogger. It is clear, for example, that the
424, Reviews—FPirsson’s Text-Book of Geology—
Cornbrash and Kelloways rock of Yorkshire are not exactly con- temporaneous with the strata bearing the same names in the South of England, while the Grey Limestone series appears to belong to the Blagdeni zone of the southern district.
The chapter on glacial deposits contains a clear and concise summary of Professor Kendall’s views on the modifications of the drainage system of the district during the Ice Age. These are accepted almost in their entirety, with the reservation that ‘‘in certain cases it may be questioned whether the existence of extra- morainic lakes can be proved, and whether the streams at the margin of the ice-sheet would not in themselves be sufficient to excavate the channels”. This is scarcely to be regarded as an improvement on the original theory: since one of the strongest arguments brought forward by Professor Bonney against the glacial origin of these channels is the difficulty of explaining how a stream whose position is determined by a necessarily shifting barrier like the edge of an ice- _ lobe could have excavated such clean-cut and steep-sided trenches.
The chapter on economic geology affords somewhat melancholy reading, since it is in the main a record of extinct industries, such as the manufacture of alum and the working of jet; while, un- fortunately, the great ironstone beds of the Middle Lias of Cleveland thin out almost to nothing before they reach the boundaries of the area here described, and the Dogger or Top Seam is for the most part represented by sandstones.
This memoir will be heartily welcomed by all who are already acquainted with the geological features of one of the most interesting districts in the kingdom, while those who wish to acquire this knowledge will find it a mine of accurate and clearly expressed information on all sides of the subject. |
R. H. Rasratt.
Il.—A Trxr-Boox or Grotoey. Part 1: Puysrcan Guotocy. By Louis V. Pirsson. pp. vili+ 444, with frontispiece, 317 figures in the text, and Geological Map of North America. New York, John Wiley & Sons, Inc.; London, Chapman & Hall, Ltd. 1915. Price 10s. net.
'W\HIS treatise on geology will, on completion, consist of two parts,
the first of which—the one now before us—is by the well-known professor of physical geology in the Sheffield School of Yale University, while the second, under the title of Historical Geology, is to be from the pen of his colleague in the chair of paleontology, Professor Charles Schuchert. Professor Pirsson tells us in his preface that it has been his aim to hold the balance even between physiography, which is the most popular side of the volume and the one most ordinarily studied, and the physical and chemical aspects, which form the real basis of the subject, and he has—we feel no hesitation in saying— successfully achieved his object. The task of the student of geology is akin to the detective’s; he has to take the evidence as set before him, and can rarely reconstruct past events. For thatreason, in geology theories have been put forward every whit as fantastic as ever
Part I: Physical Geology. 425
sprang up on the discovery of some sensational and mysterious crime. The increase in the power and range of the modern laboratory has, however, enabled many crucial problems to be isolated and studied in careful detail, and much real progress hasbeen made. The application of the principles of physical chemistry has thrown an illuminating light upon the question of the mode of formation of both igneous and sedimentary rocks. Thus, van t’ Hoff and his school have, by their classical researches, cleared up the difficulties that at one time puzzled the student of salt deposits, and the important series of investigations which have for some years past been carried out at the Geophysical Laboratory of Washington upon the conditions under which some of the important and refractory mineral constituents of rocks crystallize out are gradually unravelling the tangled problem presented by the igneous rocks. So much has been accomplished that a new textbook by one who has been so closely in touch with the trend of modern investigations is heartily welcome, and this volume is one which we can thoroughly recommend, not only to the student, but also to the general reader. The author, following a custom which has been extensively followed in recent American textbooks, makes skilful use of two sizes of type, the larger for the more general and important statements, and the smaller for additional or subsidiary detail. We must not omit a note of praise for the numerous excellent illustrations which considerably enhance the value and interest of the book. :
Part i of the complete textbook comprises two main divisions: I, Dynamical Geology, and II, Structural Geology. The former, which, as its title indicates, deals with all that has played a part in fashioning the crust of the earth into the form in which we know it to-day, is subdivided into ninechapters. The first is devoted to the atmosphere and its work, and the second to the closely allied subject of rain and running water; the air has powerful mechanical and -chemical action, and the water precipitated from it produces rivers, which carving out paths for themselves bear material to the oceans. In the third chapter we read of lakes and interior drainage, and in the fourth of the ocean and its work; as a geological factor the sea acts in much the same way as inland waters, but, of course, on a very much bigger scale, the agencies being currents, tides, and waves. An extremely interesting chapter follows on ice as a geological agent. The contrast between the eroding effect of ordinary weathering and running water and that of glaciation is well shown by three excellent sketches. The final four chapters treat successively ef underground water, organic life and its geological work, igneous agencies, and lastly movements of the earth’s shell. To human perceptions volcanoes and earthquakes are cataclysmal events, but considered from the geological point of view they are not so important as many other far less awe-inspiring agencies.
The second division, on Structural Geology, which is a little shorter than the first, opens with an introductory chapter on the general structure and properties of the earth. In the discussion of rocks and ore deposits which fills the rest of this division Professor Pirsson not only does not use, but does not even refer to, the ambitious chemical
4.2.6 Reviews—The Geophysical Laboratory.
classification of which he was one of the four authors. He still keeps to the old groups of rocks—sedimentary, igneous, and meta- morphic—which have long figured in textbooks; no doubt the wisest course to follow, since, although that arrangement is logically indefensible, petrologists have as yet come to no general agreement on a better one to replace it. The discussion is clear and well expressed, and is rendered very much easier to follow because of the many well-drawn diagrams. In an appendix the most important rock- forming mineral species are briefly described, and a copious index brings the book to a close.
Ill.—Tse Geropuysicat Lasoratory.
(]\HREE further papers, dealing with the equilibrium of the systems
occurring in igneous rocks, have recently been published. In the first of these! the system albite-anorthite-diopside is considered and the equilibrium conditions determined. This system includes mixtures which are comparatively close to certain simple types of igneous rocks such as diorite, gabbro, and basalt, and the results, therefore, are of great interest in petrology. Of the three binary systems concerned, two are eutectiferous and the third conforms to Roozeboom’s “‘type [’’. The ternary composition-diagram consists of two fields, diopside and plagioclase, separated by a single boundary curve, and there is no eutectic point. The latter fact practically precludes the possibility of any of the above-mentioned rocks representing a eutectic, and the replacement of diopside by complex pyroxene mix-crystals renders the possibility still more remote. This point is of great importance in the theory of erystallization- ditferentiation, while at the same time it negatives the suggestion that ‘ophitic’ structure represents a eutectic one. The composition of the plagioclase which crystallizes out varies not only with the original composition of the liquid but also with the rate of cooling. If the latter is not sufficiently slow for the continual attainment of equilibrium, zoning tends to occur, there being a certain rate at which the tendency is a maximum and beyond sairoln it diminishes, until in very rapidly cooled melts it may be absent.
The second paper? deals with the system lime-alumina-magnesia, and, as might be expected, is of more-importance in the study of Portland cement clinker than in petrology. The chief points of interest are the discovery of a new form of alumina (B-A], O.), which appears to be monotropic with respect to corundum (a—Al, O,), and the existence of an almost continuous series of solid solutions between the latter and magnesium spinel. The presence of comparatively large amounts of alumina does not seem to affect the optical properties of the spinel to any appreciable extent.
The third paper® contains a critical review of previous work on the
1 N. L. Bowen, ‘‘ The Crystallization of Haplobasaltic, Haplodioritic, and Related Magmas’’: Amer. Journ. Sci., ser. IV, vol. xl, pp. 161-85.
2 G. A. Rankin & H. E, Merwin, ‘ The Ternary System Ca O- Als O3s-Mg 0”: Journ. Amer. Chem. Soc., vol. xxxviii, pp. 568-88, 1916.
3 J. Johnston, H. BE. Merwin, & EH. D. Williamson, ‘‘ The several Forms of Calcium Carbonate”? : Amer. Journ. Sci., ser. IV, vol. xli, pp. 473-512, 1916.
Reviews—United States Geological Survey. 427
various forms of calcium carbonate as well as an account of much new work regarding the conditions under which each form tends to occur. It is shown that under ordinary conditions there are only three definite modifications of the anhydrous salt, calcite, aragonite, and p-CaCO,, and one hydrated form, the hexahydrate. The various other forms, such as vaterite, conchite, and so forth, are proved to be varieties of either calcite or aragonite. Calcite is the stable form at all ordinary temperatures, but appears to undergo a reversible transformation at 970° to a closely similar modification a—Ca COs. Both aragonite and «—Ca CO, are metastable under ordinary conditions and tend to pass over to calcite. The rate of the irreversible transformation of aragonite to calcite increases with the temperature, but is very slow at ordinary temperatures. There is no experimental evidence for or against the view that aragonite is the modification stable below zero or under high pressures. The conditions under which the unstable forms precipitate are practically unknown, but the factors favouring their formation include a high degree of supersaturation, the presence of nuclei of isomorphous salts, the presence of sulphate in the solution, and the action of certain organic agencies.
The paper also includes a critical examination of the various methods of distinguishing calcite and aragonite. The cobalt nitrate test, when used alone, is unreliable, as so many other minerals give the same reaction as aragonite and the effect of small quantities of impurities is so great. A similar conclusion is reached with regard to the ferrous sulphate test as well as in those advocated by Thugutt & Niederstadt, where the chief factor which influences the
result seems to be the state of division of the material. The authors conclude that the chemical tests are, in general, unreliable and should be substituted by optical ones, which only fail when the material is sub-microscopic.
Je 5
ITV.—Unitep Srarrs Geotocicat Survey.
“‘DULLETINS Nos. 620 and 621 of the United States Geological Survey constitute Parts I and II of Contributions to Economic Geology, 1915. It is pointed out that there will be no volume corresponding to 1914, because commencing with the present volume the date is that of publication, and not the year in which the field-work concerned was done. ‘The papers in part i relate to minerals and oils, and in part ii to coal and oil. Mr. G. R. Mansfield describes the nitrate deposits in Southern Idaho and Eastern Oregon, which were first discovered in the spring of 1914 in or near the canyon of Sucker Creek, about 16 miles south-west of Homedale, Idaho; deposits have also been found at Jump Creek, about 10 miles further east. The nitre occurs, associated with sodium sulphate, in veins in rhyolitic Le but not in sufficient quantity to justify working on a commercial scale. Mr, Edward L. Jones, jun., briefly discusses the gold deposits near Quartzite, Arizona, close to the Colorado River Indian
428 Reviews— United States Geological Survey.
Reservation. Placer mining started at La Paz as early as 1862, but was almost entirely abandoned a few years later. The placer areas in Dome Rock Mountains and Plomosa Mountains are composed of intrusive igneous rocks, some of schistose character and others of holocrystalline granitic texture. The schist is believed to be of pre-Cambrian, and the granite probably of Mesozoic age. The belt of cinnabar deposits described by Mr. Adolph Knopf is situated in the heart of the Pilot Mountains, about 8 miles south-east of Mina, Esmeralda County. They came to light in June, 1913, but there were signs of much earlier exploration. The main area comprises the hill now known as Cinnabar Mountain, which is composed of. limestones interstratified with dolomitic greywacke. The limestones carry crinoid fragments and other obscure fossils, and are probably of Paleozoic age; the cinnabar is intergrown with calcite and dolomite. Northwards greywacke, slate, and chert form the country rock ; here the mineral occurs in a gangue of barytes. Other deposits are situated 6 miles east of Beatty, Nye County, in the Fluorine mining district, partly on Bare Mountain and partly on Yueca Mountain. The general country rock is a fine-grained grey dolomite, of Silurian age, which is massively bedded and much distorted. Cinnabar is associated with opal and alunite. The genetic relation of the cinnabar deposits to the many gold deposits scattered throughout the Western Nevada quicksilver belt constitutes an interesting problem for future research.
Mr. Ernest F. Bouchard describes the iron-ores in Cass, Marion, Morris, and Cherokee Counties, Texas, and also the iron-bearing deposits in Bossier, Caddo, and Webster Parishes, Louisiana. In the first instance the surface rock formations consist chiefly of sand, clay, gravel, and silt. The most recent deposits are of Quaternary age, but the main masses which contain the iron-ore deposits are of early Ternary age (Eocene). he limonite deposits in Louisiana occur mostly in unconsolidated sandy clay and sand, which may be assigned to the St. Maurice formation of the Claiborne group (Eocene).
A reconnaissance of the Cottonwood—American Fork mining region, Utah, made by Mr. B.S. Butler and Mr. G. F. Loughlin, is a description of the ore deposits which will be included in a general report on the entire State, but has been issued separately in advance on account of the exceptional interest now being shown in the region. The silver-lead mines, which were discovered in 1864 and have been worked intermittently ever since, have proved very productive, but the heavy working expenses have previously militated against their success. The sedimentary rocks may be divided into two main groups—the quartzite and shale series, of pre-Cambrian and Cambrian age, and the great limestone series, which is mostly of Mississippian (Lower Carboniferous) age. The two main intrusive bodies of igneous rocks are the Little Cottonwood stock of granodiorite on the west, and the Clayton Peak stock of quartz diorite on the east of the region. The structure of the district is complex, and is characterized by considerable faulting. As a general rule the greatest mineralization occurs towards the top of the intrusive stocks
Reviews—United States Geological Survey. 4.29
or in the adjacent sedimentary formations at a corresponding horizon. Mr. G. F. Loughlin describes the recent alunite developments near Marysvale and Beaver, Utah. The feasibility of extracting potassium sulphate from alunite, which is the double sulphate of aluminium and potassium, was demonstrated by Mr. Waldemar T. Schaller, and there appears to be good hope of utilizing it as a commercial source of potash salts; also the alumina obtained as a by-product may prove of commercial value. All the deposits as yet found seem to be veins cutting porphyry (altered dacite); the veins are distinctly banded, nearly pure alunite alternating with quartz.
Mr. Edson S. Bastin and Mr. James M. Hill report on the economic geology of Gilpin County, Colorado. The ores are divisible into five groups: (1) gold-silver ores, the main economic resource of the region; (2) uranium ores, interesting as a source of radium; (3) tungsten ores, forming the basis of the tungsten industry of Beaver County; (4) copper ores, poor in precious metals; (5) titaniferous iron ores, of no commercial value. The entire area is underlain by the pre-Cambrian rocks constituting the core of the Front Range. Probably in early Tertiary time igneous rocks of many varieties were intruded as dykes or stocks. Surface deposits formed by glaciers or streams are the only other formations present.
Mr. W. T. Schaller writes upon cassiterite in San Diego County, California. The pegmatite dyke yielding the cassiterite crops out on the east side of Chihuahua Valley, about two miles south of the boundary between Riverside and San Diego Counties on the edge of the gem district.
In the second part Mr. C. E. Lesher describes a compact and convenient field apparatus for determining ash in coal, which weighs, inclusive of the case, about thirty-four pounds, and measures about a foot cube.
The Healdton oil-field, Carter County, Oklahoma, discussed by Mr. Carroll H. Wegemann and Mr. Kenneth C. Heald, was discovered in August, 1913. The oil has probably been derived from the Pennsylvanian rocks underlying the Permian Series. The accumu- lation of oil is undoubtedly due to the presence of rock folds. Mr. Wegemann also treats on similar lines of the Loco and Duncan gas-fields in Stephens or Jefferson Counties, Oklahoma. Mr. Eugene Stebinger investigated the geology and coal resources of Northern Teton County, Montana. The coal, which is of medium bituminous grade, occurs in the Two Medicine and the St. Mary River formations. The former with the underlying Virgelle sandstone is identical with the rocks called the Belly River series by Canadian geologists. Fossils are abundant, and include vertebrate, plant, and molluse remains of many species. The rocks of the St. Mary River formation consist mainly of clay and clay shale, and partly of consolidated sand. Bone fragments of undetermined Dinosaurs are abundant. Mr. Charles T. Lupton describes the oil and gas near Basin, Big Horn County, Wyoming, and Mr. D. Dale Condit the structure of the Berea oil sand in the Woodsfield and Summerfield Quadrangles, Ohio. In the latter instance, the rocks at the surface are included in the Conemaugh and Monongahela formations of the Pennsylvanian
430 | Brief Notices.
series or the Washington formation of the Dunkard group of the Permian series.
V.—Brier Noricss.
1. Tue Georoeican Structure oF THE Soura Lancasuire Coat- FIELD.—In a paper read before the Manchester Geological Society and published by the Institute of Mining Engineers (Trans. Inst. Mining Eng., vol. 1, pt. 11, pp. 328-50), Dr. Hickling discusses the general structure of the South Lancashire coalfield, with special reference to the possible occurrence of coal at workable depths below the Permian and Triassic rocks. It is shown that the structure of the coal-basin is remarkably complex, owing to the large number of folds and faults which traverse it. By much patient work this structure has been to a large extent unravelled, and the very important conclusion is reached that a large area of Middle Coal-measures exists to the south and south-west of Manchester, under a cover of Permian and Triassic rocks, which in all probability is not too thick to prevent profitable working. This should lead to important developments in the not far distant future. A second paper by the same author read at the same meeting deals with a small inlier of Lower Coal-measures in Croxteth Park. The result of trial borings was disappointing, as there was no workable coal.
2. Tunesten Ores.—In a paper read before the Chamber of Mines of the Federated Malay States in March last Mr. J. B. Scrivenor gives an account of the occurrences and production of tungsten ores in that region. The tungsten occurs in association with tin ores, chiefly as wolframite, with some scheelite. The wolframite is separated from the tin ores by magnetic processes, but scheelite is non-magnetic and some loss occurs in this way. Unfortunately the outputs are stated only in local weights, pikuls, which convey nothing to the ordinary reader. As to the genesis of the ores, it is clear that they are products of pneumatolytic modifications of granite, and in the case of the scheelite of limestones. There seems to be every reason to believe in the possibility of a largely increased output of these ores, which are now in great demand owing to the War.
3. Sprcrat Reports on THE MineRaL Resources or Great Briain. (Memoirs of the Geological Survey.)—The fourth volume of this useful series is devoted to Fluorspar. This mineral has become of considerable importance of late years as a flux in the metallurgy of iron, and large quantities are exported from Britain to the United States. Hitherto the chief source of supply has been the waste-heaps of lead-mines in Derbyshire and Durham, but these are becoming exhausted, and the question now arises to what extent it would be profitable to mine fluor-spar for its own sake. In this memoir descriptions are given of every known occurrence in this country. There would appear to be a possibility of considerable future development. At the present time it is of special importance that | a search should be made for fluor-spar of sufficiently good quality for optical purposes, which is now exceedingly scarce and commands a very high price. The fifth volume contains an account of the production in the British Isles of the following useful minerals:
Obituary—Edgar Albert Smith, I.8.0. 431
potash-felspar, phosphate of lime, alum-shales, graphite, molybdenite, chromite, talc, and diatomite. In connexion with this list the most pressing need is the discovery of some process to render easily available the vast stores of potash existing in the felspars of the igneous rocks, in order to make this country independent of the German supply of potash salts. Of most of the minerals on this list the British output is now exceedingly small, owing to free importation of foreign material.
4, Tue Vorcanic Rocxs or Sourn-EasterRN QuEENSLAND. (Proc. Roy. Soc. Queensland, 1916, pp. 105-204.)—In this paper Mr. H. C. Richards gives a very interesting account of the volcanic rocks of the south-eastern corner of Queensland, which he shows to be probably of Tertiary age. The rocks are divided into three series, lower, middle, and upper, which are in the main basaltic, rhyolitic, and andesitic respectively. The general composition is clearly sub-alkaline; only in the middle division is there a small proportion of alkaline lavas, pantellerites, comendites, and trachytes, rich in egirine, arfvedsonite, and riebeckite. These appear to be due to differentiation in the parent magma rather than to assimilation of calcareous material, as advocated by Jensen. The most strongly marked chemical characteristic in all groups is a deficiency of alumina, with a compensating excess of iron oxides. The eruptions were chiefly of the fissure type, though some of the acid eruptions have given rise to tuffs and agglomerates. Contrary to the generally received opinion the Tertiary eruptives of this area constitute a well-marked _ sub-alkaline province, with only local alkaline episodes. The earth- movements connected with the eruptions are all of the plateau- ‘building type, and there has been no folding since Paleozoic times.
OBITUARY.
EDGAR ALBERT SMITH, I.S.O.,
Lare ConcHotoeist oF THE British Museum.
BorRN NOVEMBER 29, 1847. DIED JULY 22, 1916.
Onze of the ablest conchologists of the day has recently passed away in the person of Edgar Albert Smith, who was for more than forty years on the staff of the British Museum. He died at his Acton residence on July 22, in his 69th year. His father was the late Mr. Frederick Smith, a well-known entomologist, and Assistant Keeper of Zoology in the British Museum, Bloomsbury.
Mr. Smith entered the British Museum in 1867, becoming i in due course an Assistant Keeper of the Zoological Department, and finally retiring, under the age clause, in 1913. His earlier work at the Museum comprised the arrangement of the famous Hugh Cuming collection of Mollusca, besides which he supervised for some time the whole of the marine invertebrate collections, with the exception of the Crustacea. He was chiefly responsible, however, for the arrangement of the Shell-gallery, which involved considerable care and attention, especially during that period when the natural history collections
432 Obituary—Dr. Pierre Marie Henri Fischer.
were transferred from their old home at Bloomsbury to the new museum in Cromwell Road. Mr. Edgar Smith’s researches resulted in the publication of some 800 separate memoirs on the Mollusca, and a few dealing with the Echinodermata; one of his better known works treating of the Lamellibranchs collected by the Challenger Expedition. The molluscan faunas of the great African lakes also claimed his attention and formed the subject of a presidential address before the Malacological Society of London, in which no support was given to the views of Mr. J. E..8. Moore, who regarded the Tanganyika Gastropoda as representing forms which had their origin in marine Jurassic times.
Mr. Smith had some slight connexion with geological work, as he was appealed to on more than one occasion to determine molluscan remains found in the post-Pliocene deposits of South Africa, when the majority of the species could be referred to recent forms; such determinations are to be found in the Trans. Geol. Soc. South Africa, vol. xii, pp. 112-18, 1910, and in the Ann. Rep. Geol. Com. Cape of Good Hope, 1899-1900, p. 61, and in the same journal for 1906, p. 203. He was also joint author with R. Bullen Newton of a paper “ On the survival of a Miocene Oyster in Recent Seas’’, published in the Records Geol. Surv. India, vol. xlii, 15 pp., 8 pls., 1912. He was a Fellow of the Zoological Society of London, a corresponding member of the Linnean Society of New South Wales, and of the Academy of Natural Sciences of Philadelphia. He had occupied the presidential chairs of both the Conchological Society of Great Britain and Ireland ‘and of the Malacological Society of London, being a foundation member of the latter, and editor of its Proceedings at the time of his death. For his long and meritorious services to science he was decorated, during King Edward’s reign, with the Imperial Service Order. Mr. Smith’s great knowledge of the recent Mollusca was always at the disposal of both collector and specialist, whilst his - amiable and unassuming manner endeared him greatly to all his colleagues in the British Museum.
DR. PIERRE MARIE HENRI FISCHER,
Director oF THE JoURNAL DE ConcuyLioLociz, MEMBER OF ‘THE MatacoroetcaL Socrery oF Lonpon, Ere.
BoRN IN 1866. DIED JuLY 10, 1916.
We regret to record the death of Dr. P. M. H. Fischer at his residence, 51 Boulevard Saint Michel, Paris, in his 50th year. Himself a well- known conchologist, he was the son of the eminent malacologist Paul Fischer, author of the Manuel de Conchyliologie, a translation and extension of that by the late Dr. S. P. Woodward.’ He wrote numerous important papers, and was one of the editors as well as a contributor to the Journal de Conchyliologie, from 1894 to the date of his death.
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————
I.—Norzs ON NEW OR IMPERFECTLY KNOWN CHALK Pauwaone By R. M. Bryponz, F.G.S. (Continued from the August Number, p. 3389.) (PLATE XVIII.)
HEILOSTOMATOUS Polyzoa are anything but common in the Chalk exposed on the Norfolk coast between Cromer and Wey- bourne, and which I will call the Weybourne Chalk as it is best exposed in the Weybourne half of the area. It was only quite recently that I realized that the gradual accumulation of material had produced a sufficient volume to give some idea of the general nature of the fauna. The precise position of this chalk in the zone of B. mucronata cannot be fixed on physical data, but the Survey view that it is only a little way below the Trimingham Chalk is highly probable. It is therefore rather remarkable to find that the Membranipore include several new species, in addition to IZ. flacilla (ante, p. 3388), which are unknown so farat Trimingham. It will be interesting to see if these, which I proceed to describe, prove to be characteristic of any definite range of chalk in the Norfolk Senonian. They must all be described as scarce at Weybourne.
MEMBRANIPORA FLUONIA, Sp. nov. (Pl. XVIII, Figs. 1 and 2.)
Zoarium unilaminate, adherent.
Zoeca strongly pyriporiform, very large; ‘9mm. is an average length in the centre of the zoarium, and the marginal zocecia frequently run to such lengths as 1-2 mm.: areason the whole broadly elliptical, but varying from broadly oval to practically circular, with lengths varying from an average of ‘45 mm. in the centre of the zoarium up to ‘6mm. at the margin; they occupy the bottom of cups formed by the internal front walls, which are of considerable width, and have a markedly prismatic structure, and are separated from the convex external front walls by a ridge which though obtuse-angled is often quite sharp.
Oecva prominent, sub-conical, with a slightly contracted base; free edge moderately concave.
Avicularia sub-vicarious, initiating néw rows of zocecia, large and of hour-glass type with remains of a crossbar well below the region of constriction, and the area narrowly lancet-shaped at the upper end.
DEOADE VI.—VOL. III.—NO. X. 28
434 R. M. Brydone—New Chalk Polyzoa.
Mermpranrpora FONTEIA, sp. nov. (Pl. XVIII, Figs. 3 and 4.)
Zoarium unilaminate, adherent.
Zowecia fairly large, with a tendency to angular sides, bluntly pyriporiform when occurring in established lines, and acutely so when initiating new lines; areas typically oval, with the upper end generally flattened and often indented, average length ‘5 mm., breadth -30 mm.
Owcia globular, rather elongated, with a deeply concave free edge ; aperture high and narrow. ;
Avicularia sub-vicarious, initiating new rows of zocecia, mandibular in type, much inflated laterally. :
MermBRANIPORA CUBITALIS, sp. nov. (Pl. XVIII, Fig. 5.)
Zoarium unilaminate, adherent. ;
Zowcia sub-pyriporiform, fairly large, very variable in dimensions, unusually wide, sometimes much wider than long, with sharply angular elbow-like sides; areas widely oval, flattened at the upper . end, average length -45 mm., breadth -4mm., front walls almost flat.
Owcia abundant, short wide inconspicuous swellings, the free edges of which coincide with the areal outline.
Avicularia vicarious, of the ‘Lesueurt’ type, but unusually wide and short, and with the nodal points close to the upper end of the area; they are so nearly identical in size with the zocecia and the nodal points impinge so slightly on the areal outline that it is very difficult to pick them out (there are three in Fig. 5), but a side light will catch the upturned edge of the infold of the side wall and make it stand out against the deep-lying internal front wall.
Mempranirora FuLGoRA, sp.nov. (Pl. XVIII, Fig. 6.)
Zoartum unilaminate, adherent.
Zoecia large, very shallow, with very thin side walls and no front walls at all, which gives them avery primitive aspect; average length of areas ‘65 mm., breadth ‘5 mm.; at the foot of the area there occurs very regularly a crescent-shaped cavity in the floor, round which the floor is slightly raised and which may be ocecial ; the side walls tend to expand at the bottom, and the curved part is here and there pierced by pores, which probably occur regularly though only visible irregularly.
There are no signs of external occia.
Avicularia sub-vicarious, initiating new rows of zocecia, of the hour-glass type, but hardly expanding at all below the contracted region, while above the contracted region there is a widely expanded part taking up about half the total length; the front wall is reduced to a minimum, and they are practically all side wall and area; in the lower two-fifths of the area the floor is at a lower leyel than in the upper three-fifths, and from the centre of the edge of the upper floor a narrow tongue runs down to the lower floor; remains of a crossbar occur at the lower end of the constricted region. This species has an interesting general resemblance to If. faustina (ante, p. 337).
Chalk Polyzoa.
G. W. Tyrrell—Petrography of South Georgia. 435
MemsBranipora FURINA, sp.nov. (Pl. XVIII, Fig. 7.) Zoarium unilaminate, adherent. age a Zoecia small, pyriporiform whenever they are not called upon to support an ocecium for a preceding zocecium; areas elliptical, average length -32mm., breadth ‘2mm.; many of the zocecia are closed by a slightly convex lid, in the centre of which, ina small depression, there is a tiny semicircular aperture surrounded by a faint rim; itis of course possible that these are not zocecia but avicularia, but I prefer to regard the lids as analogous to those of Lscharina(?) intricata, Lonsdale,’ especially as they occur freely in established lines of zocecia.
Oecia abundant, ground-plan semicircular (no perfect specimen yet found).
Avicularia very scarce, small sub-vicarious examples of the simple hour-glass type.
This species is relatively abundant.
EXPLANATION OF PLATE XVIII. (All figures x 12 diams. All figured specimens from Weybourne.) Fie. : 1, 2. Membranipora fluonia, sp. nov. 3,4. M. fonteia, sp. nov. M. cubitalis, sp. nov. | M. fulgora, sp. nov. M. furina, sp. nov. - (To be continued.)
SE
IJ.—Fourruer Notes on tHE PrerrocRapHy oF SourH Grorelia.
By G. ‘ie TYRRELL, A.R.C.Sc., F.G.S., Lecturer in Geology, Glasgow University.
f{\HE new material on which this paper is based has lately been received through Mr. D. Ferguson, who recently investigated the geology of the island, and collected the rocks described in an earlier paper.” It consists of twenty-seven rock specimens from the south-eastern end of the island, between Cape Disappointment and Cooper Island, and nine specimens from Gold Harbour on the north- east coast between Cooper Island and Royal Bay. All these were collected by the staff of the South Georgia Co., Ltd., under the instructions of Mr. Th. E. Salvesen, managing director, of Leith. Furthermore, by the kindness of Professor L. V. Pirsson, of the Sheffield Scientific School, Yale University, I have been enabled to examine a few beach pebbles collected from South Georgia in 1871 by R. W. Chappell, a whaling captain. These consist mainly of slates and phyllites, with sheared, faulted, and quartz-veined greywackes, probably belonging to the Lower Division of the Cumberland Bay Series. ‘There is also a rounded pebble of a fresh vesicular lava of unusual composition which is described later in this paper.
1 Dixon’s Geology of Sussex, p. 316, pl. xviii B, figs. 8, 8a, 8b. 2 GEOL. Mac., Dec. VI, Vol. I, pp. 53-64, 1914; Trans. er Soc. Hdin- burgh, vol. 1, pt. iv, pp. 797- 836, 1915,
436 G. W. Tyrrell—Petrography of South Georgia.
The sedimentary rocks in Mr. Ferguson’s collection are as follows: Between Slosarczyk Bay and Cape Disappointment there are found siliceous slates, and phyllites with vein-quartz and lenticles of erystalline limestone, in all respects similar to the types found in the Lower Division of the Cumberland Bay Series. Phyllites with quartz veins also occur on Cooper Island. In Slosarezyk Bay occurs a horn- felsed shale with peculiar clots of epidote, which is clearly associated with the epidotized rocks described later.
The Gold Harbour rocks are mainly sedimentary and are of some interest. There is a hard, green, quartzitic arkose, composed of extremely angular grains of quartz and felspar in about equal quantities. ‘lhe felspar is mainly microperthitic orthoclase, with some microcline, and varies considerably in freshness, but the turbid altered fragments are dominant. There is a little scattered chlorite, and some fine-textured siliceous matter which acts as cement. The rock is clearly an arkose derived immediately from a granite. It is entirely unsheared, and its interest lies in the fact that it supplies an original material for the puzzling ‘‘sheared felspathic grits”, ‘‘ augen-erits’’, and ‘‘ porphyroids’’ (Nordenskjold) described in the earlier paper.t Several of these rocks occur in Gold Harbour. Their mineral composition is identical with that of the arkose described above; but the quartz has been crushed down to a fine-grained granulitic paste, which forms the groundmass to numerous augen of felspar. The latter are outlined by dark, indefinite, wavy lines, consisting mainly of greenish micaceous material. Recrystallization has begun in the rock, resulting in the production of innumerable flakes of sericite interpenetrating with the quartz of the groundmass.
T'wo specimens from Gold Harbour are probably sheared acid tuffs, somewhat similar to those described in the earlier paper.” They are hard to separate from the sheared grits, but the augen texture is not so well developed, quartz is much less abundant, and the felspar has frequently not been aligned with the foliation. One of the rocks
approaches a slate in appearance. The cleavage is interrupted by °
numerous augen of fresh orthoclase, and a few of oligoclase; and also by a few rock fragments, one of which is clearly a trachyte. This rock is therefore close to the trachytic tuffs described previously, although it appears to contain more sedimentary material than they. Finally a phyllite interbedded with grits, and a coarse conglomeratic quartzite rock impregnated with pyrrhotite, may be noticed from Gold Harbour. ‘The latter rock contains a large quantity of chlorite inter- leaved with brown biotite, and has the appearance of having suffered thermal metamorphism. All the above-described rocks probably belong to the Lower Division of the Cumberland Bay Series.
The igneous rocks may be classified as follows: (1) Epidiorite ; (2) Ophitic dolerite and basalt; (8) Alaskite; (4) Quartz-felsite, with spherulitic and non-spherulitic varieties; (5) Lavas and tuffaceous rocks of doubtful affinities, and epidosite; (6) Augitite.
1 Tyrrell, ‘‘ The Petrology of 8. Georgia’’?: Trans. Roy. Soc. Edinburgh, vol. 1, p. 825, 1915. 2 Tbid., p. 827.
. i I ‘
G. .W. Tyrrell—Petrography of South Georgia. 487
1. Lpidiorite (Meta-dolerite).—This is a medium-grained greenish rock occurring in Gold Harbour. In thin section it shows large irregular plates of a pale hornblende in ophitic relations with numerous small laths of labradorite. There is a quantity of interstitial, probably secondary, quartz and leucoxenic material. The rock is obviously derived from an ophitic dolerite, but the original augite has been changed to hornblende. The latter mineral has only a slight pleochroism from almost colourless to a pale apple-green. The rock has suffered some crushing as evidenced by lines of granulitized material, and by the occasional fracture of the felspar laths. It is probably to be correlated with the decomposed ophitic dolerite described from Mr. Ferguson’s original collection,’ and is no doubt also a sill in the Lower Division of the Cumberland Bay Series.
2. Ophitie Dolerite and Basalt.—These rocks occur in Larsen and Slosarezyk Bays, and also along the coast between Slosarezyk Bay and Cape Disappointment. In hand specimens they are dark, fine- grained rocks, mottled black and white, and with an ophitic texture obvious upon inspection. In thin section the rocks are seen to consist of a plexus of plagioclase laths in ophitic relations with irregular plates of a pale purplish augite. There is also a quantity of green alteration products derived from the pyroxene, and subordinate iron- ores. The felspar gives symmetrical extinction angles in the neigh- bourhood of 30 degrees, and is therefore an acid. labradorite (Ab, An,). Zoning is not conspicuous, and when it occurs there is only a slight change in the composition of the felspar, which becomes andesine (Ab, Ang) on the margins of the crystals. The augite forms small anhedral plates of the same order of magnitude as the ‘felspar. Consequently it does not often entirely enclose the felspar laths, but is merely indented by their terminations. It is almost colourless, but frequently becomes a pale brown or purplish-brown towards the edges of the crystals and slightly pleochroic. While the ‘bulk of the mineral is fresh it is changing along the margins to a pleochroic variety of chlorite. Some sections of this substance show a good cleavage, and strong pleochroism from bluish-green to pale yellow. The mineral gives a nearly uniaxial figure, and is probably to be referred to the penninite variety of chlorite. It has suffered much solution and redeposition, and has consequently migrated into the fissures and cavities of the other minerals, especially into the felspars, which are sometimes well reticulated with thin films of chlorite along their cleavage planes. The iron-ore is rather sparse, irregular, and skeletal in form, and is titaniferous, since it gives rise to a grey leucoxenic alteration product. It is usually enclosed in the augite, especially near the margins of the crystals. There is a notable absence of apatite in these rocks.
The quantitative mineral composition of these dolerites is easily obtainable by the Rosiwal method, and is as follows: Plagioclase (Ab, An,), 42°0; augite, 36:7; chlorite, 13:5; iron-ore (titaniferous magnetite), 5°6; pyrite, 2°2 per cent. As is usual with ophitic dolerites the rock is mafelsic (i.e. the felsic constituents are roughly
1 Tyrrell, op. cit., p. 830.
438 G. W. Tyrrell—Petrography of South Georgia.
equal to the mafic), and the felspar and augite are developed in approximately equal quantity.
There is no information as to the field occurrence of these rocks, but their microscopical characters.suggest that they probably occur as small intrusive bodies, such as dykes and sills. ‘his impression is strengthened by the presence in the collection of an ophitic basalt which is almost certainly the contact-facies of one of the dolerites. The mineral composition of this rock is identical with that of the dolerites, but it has a much finer grain. There is also a distinct increase in the proportions of augite and leucoxenic iron-ore, whilst
the rock is impregnated with pyrite. The augmented proportions of
the mafic constituents, and the finer grain, supports the view that this rock: is the contact-facies of the dolerite. It is recorded as having been obtained from the coast between Slosarezyk Bay and Cape Disappointment. Doleritic rocks so much decomposed as to merit no further description were collected in Larsen and Slosarczyk Bays.
3. Alaskite.—This name was given by Spurr to an Alaskan granitic
rock consisting essentially of quartz and alkali-felspars, and practically
devoid of ferromagnesian constituents... The rock may also contain a little soda-lime felspar and muscovite. A rock of this type occurs in Cooper Island, off the extreme south-eastern end of South Georgia. In the hand-specimen it is a granular white rock with a very few dark specks representing decomposed biotite. The thin section shows that the rock consists of a granular mixture of quartz and orthoclase. Some of the latter shows mottling between crossed nicols, due to an admixture of the albite molecule, but most of the orthoclase is perfectly uniform and may be regarded as comparatively pure. Occasionally there is a granophyric intergrowth between orthoclase and quartz. ‘The only other constituents are oligoclase in very small amount, and a very few flakes of decomposed biotite.
The quantitative mineral composition of the rock, as estimated by the Rosiwal method, is as follows: Quartz, 31°9; orthoclase, 65°6; oligoclase (Ab, An,), 2°3; biotite, -2. The rock is therefore practically holofelsic. It corresponds well with the mineral com- position (by norm) of the Alaskan types. In three analyses of the latter? the quartz ranges from 40:1 to 32-9, the total felspar from 559 to 63°8, and ferromagnesian constituents from 1:1 to 2:4 per cent. The South Georgian occurrence is therefore slightly less quartzose than the typical Alaskan rocks.
4. Quartz-felsites.—These are compact white, grey, or yellowish rocks in which a minutely nodular or spotted appearance may be frequently seen. These rocks are abundant in Slosarezyk, Larsen, and Drygalski Bays at the south-eastern extremity of South Georgia. They may be divided into two groups according to whether they are spherulitic or not.
Microscopically these rocks consist of small phenocrysts of quartz and felspars in a microcrystalline to cryptocrystalline quartzose
1 Twentieth Annual Report of United States Geological Survey, pt. vil. 2 Iddings, Igneows Rocks, vol. ii, p. 453, 1913.
-
G. W. Tyrrell—Petrography of South Georgia. 439
groundmass. The latter is often abundantly spherulitic, and has undergone variable amounts of epidotization, a process referred to later. The quartz occurs in small bipyramidal crystals, the angles of which have been rounded by corrosion, and in which corrosion inlets and bays filled with groundmass are common. ‘The euhedral felspars include orthoclase, and a striped variety which has a refractive index well below that of Canada balsam and a maximum extinction angle of 14°. It is therefore a nearly pure albite. Many of the pheno- crysts are surrounded by a broad zone of felspathic material which is well marked off from the adjacent groundmass. ‘This is untwinned, extinguished uniformly, and appears to be orthoclase. It occasionally includes a number of minute quartz grains.
The groundmass is entirely crystalline, and consists mainly of minute quartz grains with a minimum admixture of felspathic material. It generally contains numerous spherulites. These are well-formed spherical bodies consisting of radiating bundles of felspathic fibres, with a subordinate amount of quartz. They are frequently built about a nucleus consisting of a crystal of quartz or felspar or, in a few cases, of a graphic intergrowth between quartz and orthoclase. The more perfect growths give a good black cross between crossed nicols. .Sometimes, however, the arrangement of the fibres is irregular and the extinction confused. This occurs mostly when there is a series of coalescent bundles or sheaves surrounding the nucleal crystal. With the disappearance of the fibrous habit and spherulitic arrangement this material can be seen to pass into the felspathic zones described above.
All these rocks contain abundant epidote. This mineral occurs ‘mainly in the groundmass and phenocrysts, but rarely invades the spherulites. Consequently, the slides frequently show a striking ‘eyed’ appearance of circular areas free from epidote, with the latter mineral dominating the concave interspaces. The epidote may also be - arranged in long streaks, and is clearly filling up small veins in the rock. In places bundles of fibrous chlorite appear along with the epidote. This process of epidotization is referred to in more detail in the next section, when more extreme products of the process are described.
5. Lavaform and tuffaceous rocks of doubtful affinities and eprdosite.— In this group is included a series of much-altered rocks, which appear originally to have been lavas and tuffs. The alteration has given rise to epidote, quartz, and chlorite, and its final term is a rock composed entirely of epidote and quartz, and epzdosite. ‘The least altered rock of the series is a tuff from the coast between Slosareczyk Bay and Cape Disappointment. The angular fragments consist of a greenish or greyish palagonitic material, faintly depolarizing, and containing small phenocrysts of felspar. There are also curious spherical amygdales of a pale-green material with a dark ring near to, and concentric with, their margins. Oligoclase (ext. 6°) is the most abundant felspar, but orthoclase is also present. Little clots of epidote are to be found within each crystal, as elsewhere in the highly decomposed groundmass of the rock, but epidotization has progressed only to a very slight extent in this rock as compared with
440 G. W. Tyrrell—Petrography of South Georgia.
those described later. From the association of oligoclase and ortho- clase in the phenocrysts this rock may be described tentatively as a trachyandesite tuff. ine
of numerous slender microlites of plagioclase felspar embedded in a turbid indeterminate base which doubtless represents original glass. The rock appears to have been an andesite glass. The groundmass now contains abundant chlorite and numerous areas of secondary quartz. Epidote is as yet confined to the large amygdales consisting of an intergrowth of granular epidote and chalcedonie silica.
In the next stage the groundmass is entirely changed to epidote, quartz, and chlorite, but in ordinary light the ‘ ghosts’ of the original felspar microlites are clearly visible. The replacement of the original material has taken place so gradually that the form of the microlites has been preserved. Moreover, the new-formed quartz and epidote is very turbid, as it seems to have replaced the substance of the rock without expelling the turbid dust resulting from previous atmospheric weathering. Only in veins and amygdales is the epidote and quartz free from this turbidity. Small phenocrysts of oligoclase and ortho- clase are still clearly visible in one of these rocks, but are in process of replacement by epidote and quartz.
The final stage of the process is a rock composed largely of epidote with subordinate quartz, in which only the faintest trace of the original texture remains. In this rock the new minerals are much clearer than in the one above described, as the turbid impurities, instead of being diffused as before, have aggregated into small clots. In general the epidote is euhedral towards the quartz, and’perfectly formed crystals are found completely enveloped in the latter mineral.
Epidotization most frequently represents a reaction between the lime-soda felspars and the ferromagnesian constituents of a rock, doubtless by the agency of percolating solutions aided by some degree of pressure and heat. In rocks containing plagioclase and ferro- magnesian minerals the constituents of epidote are there ready-made, and the reaction has excess silica, which crystallizes as quartz for a bye-product. In the rocks above described, especially the quartz- felsites, it is improbable that the constituents of epidote could have been drawn entirely from the elements of the rock. The great amount of epidote in some of the quartz-felsites shows decisively that the mineral could not have been formed from the meagre amount of lime, iron, and alumina available in these rocks. The inference may therefore be drawn that most, if not all, of the epidotic material has been brought in from the outside by percolating solutions. The progressive epidotization described above supports this view, especially if it be taken in conjunction with the facts that the epidote and quartz have occasionally replaced groundmass and felspars without expelling the turbidity resulting from previous weathering, and that in open spaces and vesicles they are quite free from such inclusions. The process has been one of gradual molecular replacement, without
1 Clarke, Data of Geochemistry, 3rd ed., Bull. 616, United States Geological Survey, 1916, pp. 597-8.
oy 4 Le ry, y
The next rock, showing a further stage in alteration, is composed.
E. 8. Willbourn—Alteration of Granitic Rock. 441
disturbing the texture of the replaced rock except in the most extreme instances. ;
6. Augitite.—Vhe pebble of igneous rock in Professor Pirsson’s collection is a dark, fresh, vesicular lava, with phenocrysts of a shining black pyroxene. In thin section it shows numerous small _phenoerysts of purplish augite and brown ‘basaltic’ hornblende in a groundmass consisting mainly of augite microlites, with subordinate euhedral magnetite and a colourless glassy base. The augite pheno- erysts are usually purplish in colour, but frequently become green towards the interior of the crystals. They are zoned in colour bands, differing slightly in optical properties, and enclose magnetite crystals, especially near their margins. The hornblendes are also euhedral, but are indented by the augites wherever they come into contact. They have a strong pleochroism in shades of brown. The augite microlites of the groundmass are almost colourless, and are embedded in a clear glassy substance of refractive index lower than that of Canada balsam. Therock is entirely felspar-free, and may be regarded as an augitite with hornblende. It is quite fresh and of recent appearance. It is a type of lava which is usually associated with series of alkaline character. * Conelusions.—The study of this collection unfortunately throws very little new light on the moot question of the tectonic. relations of South Georgia. The igneous rocks described are probably part of Heim’s ‘altvulcanischer’ area of the south-east end of South Georgia,’ and belong with the calcic end of the igneous series rather than with the alkalic; but rocks of a distinctively Andean type are still to be discovered. The pebble of augitite found by R. W. Chappell and received through Professor Pirsson is certainly of alkalic type, but on account of its mode of occurrence and isolated character no weight . can be attached to it. Hence the question as to whether South Georgia belongs to Suess’ ‘‘ Southern Antilles”? and is situated on a great loop connecting the Patagonian Andes with the mountains of Graham Land, or whether it is a remnant of an old sunken continental land, still remains open so far as the petrographic evidence goes.” The members of the Weddell Sea party of Sir E. Shackleton’s Transantarctic Expedition spent some time on South Georgia on their outward journey, and it is possible that their geologists found opportunity to collect data sufficient to solve this problem.
IiJ.—Pyevumatrotytic ALTERATION OF A VERY FINE-GRAINED GRANITIC Rock From Neer Sempitan, Frperatep Matay Starrs.’
By H. 8S. WILLBOURN, B.A., Assistant Geologist, F.M.S.
BOUT one mile to the north of the railway station at Ayer ui Kuning, in the south of Negri Sembilan, one of the Federated Malay States bordering on Johore and Malacca, is a low but con- spicuous range of hills covered with long grass. The highest of the
1 Fr. Heim, Zeitschr. Ges. Erdkunde, Berlin, April, 1913.
? Tyrrell, Trans. Roy. Soc. Edinburgh, vol. 1, pt. iv, p. 832, 1915. * Communicated with the permission of the Government Geologist, F.M.S.
442 H. S. Wllbourn—Alteration of Granitic Rock.
hills, on which is a beacon used by the Trigonometrical Survey,
stands about 300 feet above the level of the surrounding country. .
The general trend of the hill range is in a direction of S. 60° W. to N. 60° E., and there are several hills which branch from the main axis, usually more or less at right angles toit. The eastern half of the range over a distance of about half a mile only need be considered, as there are no rock exposures on the western half.
The framework of the hills is seen to be made up of a white, fine-grained rock, containing small iron-stained cavities, which in its usual weathered state very much resembles a fine sandstone. Examination under the microscope shows it to be a very fine-grained igneous rock, consisting essentially of quartz and mica, sometimes with felspar, and nearly always with abundant blue tourmaline. In one or two places hard fragments of silicified shale were found lying on the hills, and one exposure showed patches of shales included in the white rock. It is doubtful whether these are shales of the Raub Series, which have become non-caleareous through the ordinary processes of weathering, or whether they belong to the younger Gondwana Series, consisting of shales interbedded with quartzites and sandstones. The boundary-line between outcrops of the two series lies in the locality, but its exact position cannot be traced. From the evidence of the dislocation of occasional quartz veins which penetrate the white rock, it is seen to have undergone faulting, and this is confirmed by micro- scopical examination of the shales. However, the amount of throw of the largest fault observed is only a few inches.
A large outcrop of granite is situated to the south-west, about two miles from the Trigonometrical Survey beacon.
In a hand-specimen the hard unweathered rock is seen to be very fine-grained. It is homogeneous in appearance, except that it contains dark-blue bodies, usually not bigger than a pea, sporadically scattered throughout the rock. They look very much like blots of blue-black ink on white blotting-paper. Under the microscope the rock is seen to consist for the main part of quartz and muscovite. The quartz occurs as irregular grains of a uniform small size, one separated from another by an aggregate of still finer grain, consisting of quartz and muscovite. There are a few flakes of yellowish mica of considerably larger size which contain tiny inclusions. Some specimens of the rock seem to contain no felspar at all. An attempt was made to separate felspar from a crushed sample of the rock by using a solution of mercury potassium iodide of a density such that orthoclase would float and quartz would sink. Some specimens proved to contain no felspar at all, others contained a small quantity of orthoclase.
With still other specimens there is no need at all to use a heavy liquid in order to determine the presence of felspar, for small pheno- erysts can be seen: under the microscope. These can just be distinguished in the hand-specimen. They are of quartz, orthoclase, and plagioclase with extinction angle corresponding to oligoclase. The rest of the rock is made up of a mosaic of quartz and felspar with occasional flakes of yellowish mica, which contains inclusions.
The quartz grains in the quartz-felspar mosaic are of the same size as those in the quartz-mica rock. The flakes of mica in the former
E. 8. Willbowrn—Alteration of Granitic Rock. 443
rock appear to be identical with the few larger flakes of mica in the quartz-mica rock.
The dark-blue bodies meneioned above consist of quartz and blue tourmaline. The quartz occurs as irregular grains of the same size as those in the white quartz-felspar or quartz-mica rock which encloses the bodies.
The tourmaline occasionally shows crystal outline, then occurring as tiny prisms, but usually it occurs as shapeless grains, one of which may enclose two or three of the quartz grains. The dividing line between the quartz tourmaline bodies and the surrounding white rock is very irregular, particularly in the quartz-felspar rock, The tourmaline seems “to be replacing muscovite in the quartz-muscovite rock, and felspar in the quartz-felspar rock. The difference in the appearance of the quartz-tourmaline bodies is very striking in hand- specimens of the two rocks, for the bodies in the quartz-muscovite rock appear to have a sharp outline, and their shape is roughly spherical. They weather out in a conspicuous fashion, and in places can be found lying about on the rock surface. The bodies in the quartz-felspar rock have an irregular branching outline.
Sometimes the bodies are more or less regularly distributed throughout the mass of the white rock (quartz-muscovite or quartz- felspar), but in some exposures there is an arrangement along definite parallel planes. One specimen of quartz-mica rock collected from the east end of the hill range shows a large number of the bodies partially amalgamated to form a plate, so that a cross section has the appearance of a string of beads. Under the microscope these bodies are seen to have the same structure as those already described, and the plate, although not unlike a vein, is seen to be very different from certain true quartz-tourmaline veins which were observed in several parts of the hills, penetrating the quartz-muscovite rock. These veins are minute with a thickness of only about + to 4 of an inch. They ‘consist of long prisms of blue tourmaline set in a mosaic of clear quartz. The veins are of a very much coarser grain than the parent rock. They have sharply defined walls. Sometimes a prism of tourmaline was observed not to end abruptly at the wall of the vein, but to penetrate for a short distance into the quartz-mica rock. As soon as it left the vein, however, it lost its sharp crystal outline and enclosed the quartz grains of the quartz-mica rock, taking the place of the interstitial flakes of muscovite.
In exposures immediately east and west of the beacon hill, the tourmaline bodies are very small in size, being no bigger than a pin’s head. More often than not they are arranged along definite planes, otherwise there is no distinction between them and the larger bodies.
Two small exposures on opposite sides of the beacon hill show a rock of a shghtly coarser grain than that already described. More- over, no tourmaline can be seen in the hand-specimen. Under the microscope it is seen to be porphyritic, the phenocrysts being bleached biotite and quartz with the irregular outline characteristic of the corroded quartz phenocrysts in porphyritic rocks. In addition there are areas of secondary mica whose form suggests that they are altered felspar phenocrysts. The biotite contains needles of rutile associated
444 EH. S. Willbourn—Alteration of Granitic Rock.
with iron-ores and sometimes forming a sagenite web. It is practically uniaxial. The ground-mass consists of quartz and secondary mica. A slide cut from one specimen showed a wavy line, like a crack penetrating the rock, along which occurs some fine- grained opaque material and, at one point, a large grain of blue
tourmaline. A specimen of this rock was crushed in order to examine
the heavy minerals. Much zircon in small perfect crystals is present and also several grains of blue tourmaline.
This rock resembles an igneous rock which outcrops at the old disused gold-mine of Bukit Chindras, which is situated along the direction of the Ayer Kuning hill range (namely about N. 60° E.), and is between one and two miles distant from it.
The gold-bearing quartz veins strike in a direction approximately north and south. Mr. Scrivenor, the Government Geologist, visited the mine in 1904, shortly after it had been shut down, and he then noted (Preliminary Report on the Gold Mines of F.M.S., Kuala Lumpur, May, 1904) that the country rock is ‘‘ bleached shale. . . together with a small quantity of a pale green rock which was not seen im situ, composed of fine flakes of colourless and pale green muscovite, quartz grains, iron ores, and small prisms of rutile ”’
The rock can now be seen forming an outcrop on the hillside 70 yards long in a direction about N.W. by 8S.E. and about 20 yards wide. It is much weathered, but slides cut for micro- scopic investigation showed phenocrysts of bleached biotite, containing needle-shaped inclusions of rutile associated with iron-ores, with large corroded quartz phenocrysts, and areas of regular form filled with an aggregate of secondary muscovite which may represent felspar phenocrysts. The remainder of the rock consists of an
irregular mass of secondary quartz and mica. The rock shows-
evidence of having undergone strong shearing, and thin quartz veins penetrating the rock have also been subjected to strain. It contains a certain amount of iron pyrites, is plentifully stained with iron, and has numerous cavities.
The rocks described above bear a strong resemblance to the beresites of the Urals described by G. Rose.! He describes them as vein rocks which outcrop in tale and chlorite schists, themselves traversed by the gold-bearing quartz veins. Beresite is a very uniformly grained rock, nearly always decomposed and impregnated with iron pyrites. Itis made up of orthoclase, plagioclase, quartz, and primary mica, and these are altered to secondary mica and quartz, according to another writer, Arzruni. Some varieties resemble sericite schists, others resemble micaceous sandstones. Original rutile is present as aggregates and as inclusions in quartz. Rosenbusch? and also Zirkel* quote Helmhacker, who wrote a later description. He says that beresite is a quartz porphyry, poor in quartz, in which the felspars vary in amount, and may disappear altogether on account of their alteration to muscovite and quartz.
1 Zirkel, Petrographie, vol. ii, p. 41, 1894. i
2-H. Rosenbusch, Mikroskopische Physiographie, II Massige Gesteine, p. 462, 1896.
3 Zirkel, Petrographie, vol. iii, p. 793, 1894.
LE. 8. Willbourn—Alteration of Granitic Rock. 445
As mentioned above, the quartz-muscovite rock of Chindras is traversed by gold-bearing quartz veins, and this is another point of resemblance with beresite. The Malay headman at Ayer Kuning informed the writer that his father had got a small quantity of gold many years ago by washing the soil of the Ayer Kuning hill range, but not sufficient to encourage him to go on with the work.
The elvans of Cornwall resemble these rocks to a certain extent, but differ in that they frequently contain brown primary tourmaline and also they are coarser in grain. Regarding the alteration of elvans, Dr. Flett' says: ‘‘ abundance of fine muscovite in the ground mass of an elvan is probably a certain indication of pneumatolytic action, as muscovite is very rarely a primary ingredient of these rocks.” The formation of greisen in the elvans of Cornwall has often been accompanied by the formation of tinstone. The nearest locality to Ayer Kuning in which cassiterite is found in any quantity is at the contact of granite with sandy shales, four or five miles to the west.
The Ayer Kuning and Chindras rocks differ from ordinary greisens in two respects. Greisens are rocks consisting of quartz and white mica, usually with tourmaline and topaz as accessories. The Ayer Kuning rock contains no topaz, and the Chindras rock in addition contains no tourmaline. Also the Ayer Kuning rock differs from other described greisens in its very fine grain. The felspathic portions of it may be described as a yery fine-grained granite porphyry.”
The Grainsgill greisen* is another rock formed probably in a similar way by the alteration of felspar to white mica, and it also is like the Ayer Kuning rocks in that it is deficient in topaz and tin- stone, but the latter differ in their very much finer grain.
It seems clear from the specimens examined that all of the Ayer Kuning and Chindras rock was felspathic in the first place, and that in the greater part of it the felspar has subsequently been altered to white mica. This is suggested by the similar texture of the fel- spathic and non-felspathic rocks, although there is one difference, namely, the lack of phenocrysts in the fine-grained quartz-muscovite rock. However, the coarser quartz-muscovite rock of the beacon hill and of Bukit Chindras contains phenocrysts. The field evidence leaves no doubt that the two rocks are part of the same intrusive mass, for specimens of both the felspathic rock and the quartz- muscovite rock were collected from the same exposure.
There is good reason to believe that the quartz-tourmaline bodies are secondary structures, and not products of consolidation. Their grain is uniformly like that of the surrounding white rock, and the tourmaline, which is always the blue variety, is in the same relation to the quartz as is the secondary mica-quartz aggregate in that it is
} Mem. Geol. Survey, Land’s End District, p. 65, 1907.
* As the ground-mass is not eryptocrystalline but a fine-textured crystalline aggregate of quartz and felspar, the best term is either granite porphyry or microgranite, and granite porphyry is the better of these, because of the pheno- erysts.
Onde Giss, vols lit py 142) 1895:
446 HE. S. Willbourn—Alteration of Granitic Rock.
essentially interstitial. In the quartz-tourmaline veins which are described above the tourmaline is idiomorphic and the quartz is interstitial, but, as has been pointed out before, when one of the long prisms of tourmaline penetrates into the country rock, although the crystalline continuity is preserved, in that the crystal extinguishes as a whole, yet that portion of it in the quartz-mica rock now encloses the quartz grains, so behaving like the tourmaline in the quartz- tourmaline bodies. The arrangement of the bodies along parallel planes could be explained as a flow-structure, but none of the pheno- crysts show signs of similar orientation: so it seems to be reasonable to take it as further evidence pointing to the secondary nature of the bodies, and that where this arrangement along parallel planes exists it is due to former planes of weakness in the rock which afforded easy access to mineralizing vapours. The single grain of tourmaline observed in the coarser quartz-muscovite rock exposed on the beacon hill lay in a crack and appeared to have had a secondary origin.
Conclusion.
There is little doubt but that the rock is the result of the greisenization of a very fine-grained granitic rock, some of which has been less altered and can still be recognized as a granite porphyry. The rock, however, was not all porphyritic, and the greater part of it might have been an aplite. Perhaps the alteration of the felspar to tourmaline and the alteration to secondary mica took place in distinct operations. Some specimens of the felspathic rock appear to contain no secondary muscovite at all, yet a considerable quantity of the felspar has been altered to tourmaline. Again, as described above, some of the rock contains practically no tourmaline, and the felspar seems to be completely altered to muscovite. There is an indication that the process of tourmalinization was the later of the two. It has been noted that the quartz-tonrmaline bodies in the quartz-felspar rock are much less definite in outline than those in the matrix of quartz and muscovite. The only difference in the two rocks is that one contains much felspar and little muscovite, while the other contains much muscovite and little felspar. Presumably this difference was responsible for the difference in the quartz- tourmaline bodies, and so it must have existed before the tourmalini- zation occurred.
The origin of the Ayer Kuning rocks and that of the Russian beresites seems to have been very similar. Beresite is a quartz porphyry in which the felspars have been altered to secondary mica and quartz. The Ayer Kuning rock is the result of a similar alteration of a very fine-grained granite porphyry which passes into an aplite without phenocrysts. ‘The Chindras rock contains little or no tourmaline, but in Ayer Kuning rocks the blue tourmaline is a characteristic feature. A point of difference between these rocks and beresite is that the latter is rather poor in quartz owing to the small amount in the original quartz porphyry. ‘The Ayer Kuning granite porphyry appears to have been of normal composition.
Dr. Du Riche Preller—Ophiolithic Rocks, W. Liguria. 447
1V,—Tue Opniotiraic Groups oF THE LicguURIAN APENNINES. I. Western Liguria.
By C.S. Du RicHE PRELLER, M.A., Ph.D., M.I.H.E., F.G.8., F.R.S.EH.
‘W\HE groups of ophiolithic, that is, crystalline ferro-magnesian
rocks in the comprehensive sense, to be dealt with in this and the subsequent paper are those west and east of Genoa.’ Of these the principal western or Voltri group was already referred to in the preceding paper” as being, on its western margin, contiguous to the erystalline massif of Savona, and as constituting with the latter the geological contact-zone of the Alps and the Apennines. The anomaly of its position and petrological character is enhanced by the abrupt, clean-cut division of its eastern margin from the adjacent, more recent, and smaller ophiolithic group of Sestri and Isoverde, which is coeval with the groups of Eastern Liguria.
Tue Groups or Wrsrern Licuria. (Fig. 1.)
The border of the large and important area known as the Voltri group runs on the south, from its contact with the Savona massif near Varazze, along the Riviera to Cogoleto, Arenzano, Voltri, Pra, Pegli, and Sestri Ponente; then north up the Chiaravagna Valley, to Isoverde in the Iso Valley, to the Bocchetta Pass on the crest of the Apennines, and thence to Voltaggio in the Lemmo Valley. From here it extends, as the northern margin, across the Corrente, Stura, Orba, and Erro Valleys to near Ponzone, south of Acqui, whence it turns south to the Giovo Pass and Corona, and along the contact line of the Savona massif down to the coast at Varazze. The divide of the Apennines runs more or less parallel to the coast from the Giovo Pass (522 m.), to Mte. Ermetta (1,262 m.), Mte. Reisa (1,184 m.), the Turchino Pass (552 m.), Mte. Penello (996 m.), and the Bocchetta Pass (777 m.), so that only the southern part or about one-third of the area hes in Liguria proper, while the northern and larger part belongs to the Po watershed; in its entirety the complex, covering no less than 36 by 22 km. or 800 square kilometres, is by far the largest in the Apennines. It exceeds even that of the Lanzo Valleys in the Piemontese Alps; like the latterit has, owing to its prevalently peridotitic and serpentinous rocks, resisted denudation and hence preserved its compactness, continuity, and also its often austere aspect in aremarkable degree. The three principal roads along which, besides the coast-road, the ophiolithic and sedimentary rocks of the area may be studied, are those crossing the Apennines south to north from Varazze by the Giovo Pass to Sassello and Acqui on the west, from Genoa by the Bocchetta Pass to Voltaggio on the east, and from Voltri by the Turchino Pass to Campoligure, Rossiglione, and Ovada in the centre, to which last-named runs in great part parallel the railway from Genoa to Ovada.
! The term ophiolithic, though in its original and narrow sense it refers only to serpentines, applies to eruptive basic rocks or pietre verdi comprehensively, irrespective of age, like, e.g., the ‘ roches ofitiques’ of the Pyrenees.
2 GEOL. MAG., September, 1916, p. 400 et seq.
448 Dr. Du Riche Preller—Ophiolithic Rocks, W. Liguria. Fig. 1. Sketch Map of Voltri Group, Western Liguria.
tailways haces 1: 500,000. settee LOADS
Cs) amt o ame oe oe Apenncrest
C S=calc-schists; P V=pietre verdi; Mio=Miocene. E S=Eocene Serpentine x diabase; Eo=Eocene sedimentary.-
Trias Eocene ES er ar ane TE
~RKKK KKK KY, KARR KKK KK
=a SS
Dae
ps9) 9
») »
45 119d2956
o 91194
Fig. 2.. Contact of Trias and Eocene, Monte Gazo, Chiarayagna Valley.
Dr. Du Riche Preller—Ophiolithic Rocks, W. Liguria. 449
The Voltri group is composed almost entirely of Mesozoic, dark- grey, often talcose calc-schists, and infolded, intercalated, and over- lying pietre verdi. As such it belongs geologically to the Alpsrather than to the Apennines, and the anomaly of its position consists in its being wedged between the Savona crystalline massif at one end and - the Eocene formation at the other. Up to 1882 it was variously assigned to the Archean, Paleozoic, and, more often, to the Tertiary formations, and it was not: tiil Issel and Mazzuoli’s investigations of 1883 and 1884! that a clean-cut line of division was shown to exist north of Sestri in the Chiaravagna Valley, and thence to Isoverde between the older Triassic Voltri group on the western and the more recent Eocene ophiolithic and sedimentary series on the eastern side of that line.
The determining factor in this division was Issel and Mazzuoli’s discovery of several isolated deposits of Triassic dolomitic limestone immediately west of the line between Sestri and Isoverde, viz. on Mte. Gazo, Mte. Torbi, and Mte. 8. Carlo, and also north of the crest of the Apennines near Voltaggio, while more recently Rovereto ? elucidated those of Cogoleto and Arenzano on the coast, and Franchi’ also adduced valuable evidence of the Mesozoic age of the Voltri group. ‘These dark-grey and bluish, cavernous, sparsely fossiliferous (gyroporelle) limestones are, like their equivalents in the Maritime Alps and the Savona region, as also like the grezzoni of the Apuan Alps,‘ indubitably Middle Triassic, underlying normally the Upper Triassic cale-schist and pietre verdi horizon. The three deposits between Sestri and Isoverde present the abnormal phenomenon that they rest on serpentine and amphibolite of that horizon instead of vice versa.° This reversed sequence is, however, purely local and is due to an inverted fold along the greatly disturbed, faulted, and tilted contact of the Triassic and Eocene formations, whose marked uncon- formity is e.g. well exposed in the Chiaravagna Valley on the eastern flank of Mte. Gazo, as also in the Rio Recreusi ravine on the eastern flank of Mte. S. Carlo near Isoverde. Along the coast near
1 L. Mazzuoli & A, Issel, ‘‘ Sovraposizione nella Riviera di Ponente d’una zona ofiolitica eocenica ad una zona ofiolitica paleozoica’’: Boll. Soc. ital., 1883, p. 44 et seq. ‘‘ Zona di coincidenza delle formazioni ofiolitiche eoceniche e triassiche nella Liguria occidentale ’’: Boll. R. Com. geol., 1884, p. 2 et seq.
2 G. Rovereto, ‘‘ Questioni dei calceschisti studiata in Liguria ’’: Boll. Soc. geol. ital., 1909, p. 408 et seq. ‘‘ Schisti e serpentine antichi in Liguria ’’: Atti Soc. Ligure Sc. nat., vol. ii, 4, 1891.
3 §. Franchi, ‘* Massiccio cristallino ligure’’: Boll. R. Com. geol., 1893, p. 43 et seq. ‘‘Relazione campagna, 1911’’: ibid., 1912, p. 41. ‘‘ Posizione della zona a Helminthoidea labyrinthica nell’ Hocene superiore’’: ibid., 1915, p. 297. Franchi claimed the Voltri group as belonging to the Mesozoic calc- schist and pietre verdi horizon of the Maritime and Cottian Alps in ‘‘ Zona Pietre Verdi, Ellero e Bormida ’’, ibid., 1906, p. 89 et seq.
4 Both the Ligurian and the Apuan dolomitic limestone, independently analysed, contains 58 per cent carbonate of lime and 38 per cent carbonate of magnesia.
° This superposition Mazzuoli and Issel regarded at the time as normal. They therefore assigned the calc-schists and pietre verdi to the Lower Trias, and figured these as such in their map of Liguria of 1887. The formation is now, like that of the Piémontese Alps, recognized as Upper Triassic.
DECADE VI.—VOL. III.—NO. X. 29
450 Dr. Du Riche Preller—Ophiolithic Rocks, W. Liguria.
Cogoleto and Arenzano the sequence is normal, the dolomitic lime- stone and quartzite here being, moreover, as Rovereto has shown, underlain by Lower Triassic quartzite and conglomerate and Permian schist as the substratum. Another curious phenomenon is the wedge of cale-schist, quartzite, and mica-schist which projects from the belt of these rocks on the coast into the pietre verdi area north of Voltri for about 12 kilometres to Mele, the Turchino Pass, and beyond to Masone and Campoligure. This wedge, very similar to the Santuario island in the Savona region, is up to 4 kilometres wide, and divides the Voltri group on the Ligurian side into two unequal parts. Except an outcrop of serpentine in the Stura Valley immediately north of the road-tunnel on the Turchino Pass, it is practically denuded of pietre verdi.
The Eocene formation east of the contact line and thence to the Polcevera Valley, north of Genoa, is composed as usual of fossiliferous (Helminthoidea) limestone, argillaceous, often shaly schist, and macigno sandstone. It is in the argillaceous schist between Cornigliano and Sestri, viz. between the Polcevera and Chiaravagna Valleys, that occurs the mass of ophiolithic rocks which extends from the headland of S. Andrea north to Borzoli and Madonna della Guardia for about 8 and 2 kilometres in length and width, while further north several smaller masses crop out at S. Martino, near the Bocchetta Pass, and between the latter and Voltaggio, forming a fringe round the eastern margin of the Voltri group. As in the Savona region, so also in the Voltri area deposits of Oligocene conglomerate and breccia are frequent and extensive, one of the largest being a bank 500 metres in thickness in the Morsone Valley near Voltaggio, which is entirely composed of pietre verdi débris.
The relation of the Voltri group to the adjacent one of Sestri and Isoverde has been the aul ect of considerable controversy. De Stefani’ and Termier & Boussac® regard the Voltri group as an integral part, not of the Alps, but of the Apennines. In Termier and Boussac’s view there is between the two sedimentary and ophiolithic formations no division or discontinuity, but a gradual passage from Triassic to Post-Triassic, the former being simply more metamorphosed than the latter, and both constituting a consecutive series after the pattern of the French Alpine séries compréhensives. Sacco assigns the argillaceous schists and the macigno sandstone, including the ophio- lithic rocks of the Sestri and Isoverde group, to the Cretaceous, and the uppermost fossiliferous (Helminthoidea) limestone strata to the Lower Eocene.? The weight of evidence is, however, largely in favour of a distinct difference and division between the two un- conformably juxtaposed sedimentary and ophiolithic formations, the Voltri group being Triassic and that of Sestri and Isoverde prevaiently
1 ©. De Stefani, ‘‘ La zona serpentinosa della Liguria occidentale ’’: Rendi- conti Atti R. Acc. Lincei, Roma, 1913, pp. 547 and 661 et seq.
2 Pp. Termier & J. Boussac, ‘‘ Passage latéral N.O. de Génes de la série cristallophyllienne (schistes lustrés) 4 la série sédimentaire-ophiolitique de l’Appennin ’’?: Comptes Rendus Acc. Sciences, Paris, 1911, p. 1361 et seq.
°F. Sacco, ‘‘L’Age des formations ophiolitiques récentes’’: Bull. Soc. belge de Géol., vol. v, 1891. Carta geologica Appennino centrale 1 : 100,000, Torino, 1891.
Dr. Du Riche Preller—Ophiolithic Rocks, W. Liguria. 451
Upper and Middle Eocene. The division is shown e.g. in the interesting superficial section of Mte. Gazo in the Chiaravagna Valley (Fig. 2).
The principal constituents of the pietre verdi of the Voltri group are peridotite, lherzolite, serpentine, and euphoditic, amphibolic, eclogitic, and garnetiferous rocks. Although in some cases well preserved, they conve more generally various stages of alteration, schistosity, and decomposition, and are, moreover, so interfolded and intermixed both with each other, and with the enclosing, often talcose eale-schists that their delimination and subdivision is as difficult as in the similar case of the Lanzo Valleys. The peridotitic and serpentinous rocks alone are easily distinguished by the dark colour, the rugged outlines, and the barrenness of their outcrops, in contrast to the other pietre verdi and the cale-schists often covered with abundant vegetation.
Along the coast-road between Pegl and Pra tke headlands exhibit outerops of dark, dull serpentine and euphodite with glaucophane, in part brecciated and decomposed, alternating with shaly, talcose calc- schist which fringes the coast from Sestri to Voltri.2, North of Pegli in the Varenna and upper Gorzente Valleys appear lherzolite and serpentine with euphodite veins, and north of Pra, as also north of Voltri, in the Acquasanta ravine, occur considerable rugged outcrops of dark-green and black peridotitic rock, which from their forbidding appearance are known as the Scogli Neri and the Scoglio del Diavolo. Beyond Voltri a large mass of serpentine continues to Arenzano and Cogoleto, where it alternates with peridotitic rock and calc-schist. Between Cogoleto and Varazze a large mass of euphodite stretches north, while at Varazze the dark-green serpentine shows euphodite veins. Thus, the continuous mass of peridotitic and serpentinous rocks, with associated euphodite and alternating with calc-schist along the littoral, is interrupted only by the calc-schist wedge of Voltri and Campoligure previously mentioned.
Along the eastern margin similar outcrops of enstatitic and diopsitic lherzolite, glaucophanic euphodite, and amphibolite appear on the western flank of Mte. Gazo, while further north serpentine pre- dominates west of Mte. lines again, west of Mte. S. Carlo in the Iso Valley a lherzolitic mass exhibits euphodite veins, and lherzolite and serpentine also crop out in Mte. Persucco and Mte. Roncasci, west of Caffarella. From here extends on both sides of the Apennine erest the great euphodite mass of Mte. Lecco, probably connected with the similar mass north of Varazze in the south-western part of the area. In this, asin the other euphodite masses, the rock varies from the well-preserved diallagic to the altered type with saussurite and smaragdite, and is often gneissiform, laminated, and schistose. In the Olba Valley, north of the Apennine crest, occur considerable eclogitic masses, and along the western margin contiguous to the
' This section is deduced from Rovereto’s more extensive one, op. cit., p. 414.
2 Professor Bonney described some of the coastal rocks between Sestri and Pra in *‘ Notes on some Ligurian and Tuscan Serpentines’’: GEOL. MAG., May, 1879, p. 362 et seq.
452 Dr. Du Riche Preller—Ophiolathic Rocks, W. Liguria.
crystalline massif of Savona, the pietri verdi, which overlie the latter at Corona, present the usual varieties already mentioned.
Although the Triassic pietre verdi of the Voltri group and the Eocene ophiolithic series are both of eruptive origin, they exhibit certain differences, not of substance, but of facies and degree. ‘Thus, the older serpentines are more uniformly dark and dull in colour, the younger generally a brighter, richer, and more lustrous green, with varicoloured passages; again, the pietre verdi when schistose often pass to the infolding cale-schists, whilst the Hocene rocks are more clearly defined from the sedimentary strata. The former are more often amphibolic, the latter more pyroxenic, viz. diabasic. The serpentino-calcareous rock ‘ophicalce’ is rare in the Voltri group, but not infrequent in the Kocene series, and the same difference applies in an enhanced degree to metalliferous deposits. These differences are clearly exhibited in the Hocene ophiolithic series of Eastern Liguria, as well as in the smaller, essentially serpentinous and diabasic masses infolded in the Eocene sedimentary strata between Sestri and Isoverde and bordering on the eastern margin of the Voltri group. Among these are notably the outcrops of the 8. Andrea headland on the coast near Sestri; of S. Rocco, east of Panigara in the Chiaravagna Valley ; of Borzoli and of Madonna della Guardia at the northern end of that mass;' again, further north, those of Caffarella and S. Martino, which latter village is built on Kocene serpentine; and lastly, the Eocene serpentine with calcite veins known as ‘‘ verde di Polcevera”’ of Pietra Lavarezza, just below the Bocchetta Pass, which vies with the similar rock of Levanto in Eastern Liguria.?, Beyond the Pass Eocene serpentine and diabasic rocks appear in the Lemmo Valley near Molino di Voltaggio along the Bocchetta road and in the lower part of the Acquastriata ravine, whose upper part lies, however, in calc-schist and pietre verdi. Some further small masses near Voltaggio complete the Eocene fringe.
As regards the anomalous position of the Voltri group east of the Savona massif, there is an obvious correlation between it and the underlying dolomitic limestone, the isolated outcrops of which all round the group can only be remnants of a much more extensive and continuous formation which reached west to the Savona massif and the Maritime Alps. That formation must have been overlain by a similarly extensive one of calc-schists and pietre verdi; hence, in the intervening gap in the Savona region the two formations must either have been removed by erosion and denudation or they must have been pushed over from the Maritime Alps. The gap in the
1 Near Borzoli occurs the amygdaloidal caleareous diabase called borzolite, and west of Murta the cavernous variety called coschinolite by Issel. Madonna della Guardia is almost entirely built on diabase.
2 The serpentine of Pietra Lavarezza with associated ophicalce is overlain by diabase which forms the left bank of the upper Riasse torrent. In the Recreusi glen, where the unconformable contact of the Triassic limestone and the over- lying Eocene argillaceous schist is conspicuously exposed, occur, along the junction of the Hocene ophiolithic rocks, large masses of Triassic gypsum which are quarried near Isoverde.
W. R. Jones—Tin-mining at Ulu Bakau, F.MS. 4538
Savona region between the calc-schists and pietre verdi in the north- eastern part and those of the Bormida Valleys on the western margin is only about 15 kilometres; it may, therefore, be legitimately assumed that the gap was simply eroded, that both the Triassic formations—dolomitic limestones and cale-schists with pietre verdi— originally extended from the Maritime Alps continuously to the Voltri group, and that the latter, of submarine sedimentary and eruptive origin, was formed 7m situ rather than by an overthrust from the west. In either case itis, by reason of its Mesozoic age, geologically Alpine in character, and constitutes, together with the Savona crystalline massif, the contact-zone of the Alps and the Apennines.
V.—Munine In THE Feperatep Matay Sratss.
[In the GEOLOGICAL MAGAZINE for June last, p. 255, Mr. W. R. Jones refers to a Preliminary Report of Mining in the Mam Granite Range, Federated Malay States, 1913. This report bore a slightly different title, and was not published. It is the property of the Federated Malay States Govern- ment, but I have the permission of the Chief Secretary to forward to you a typescript marked ‘‘ Office Copy’’ and initialled by Mr. Jones, and to ask you to publish that portion of the report which refers to Gunong Bakau.— J. B. SCRIVENOR, Geologist to the F.M.S. Government.
GEOLOGIST’S OFFICE, BATU GaAJAH, July 14, 1916.]
Pretiminary Repvort on Tin-mininc on tHe Matin Ranee at Utu BaKavU AND NEIGHBOURHOOD.
Hemy’s Lode, Ulu Bakau (Sungei Bakau Mine).—At a height of about 4,500 feet tin-ore is found in this mine in undecomposed granite which has to be crushed by foot-stamps before the cassiterite can be recovered. The rock is a medium-grained granite, very rich in quartz, muscovite, and cassiterite, and relatively poor in felspar. Microscopic sections show that the greenish colour, so noticeable when the rock is wet, is due to the presence of chlorite formed by the alteration of the muscovite and pale-coloured biotite of the original granite. The rock here is very different in appearance from that in Mr. Bibby’s mine, but agrees with it in the low percentage of felspar.
An interesting point in a granite so heavily mineralized is the small amount of pyrite and mispickel on the one hand, and the abundance of tourmaline on the other. I have noticed this in other cases, and although the two classes of minerals do occur together in the same mine, yet the abundance of one class seems to be at the expense of the other class. This is well illustrated in Mr. Bibby’s mine, where one part is very rich in tourmaline and topaz, whereas the other (the one near the aerial rope-way) is extremely rich in mispickel and pyrite. The explanation is that where tourmaline and topaz are abundant, the tin-ore came up originally as the vapours _ of fluorine and boron; and where mispickel and pyrite are predominant the vapours of sulphur and arsenic were the mineralizers. So persistent is tourmaline in Mr. Hemy’s mine that the Chinese call it by a name which means “‘ the friend of tin’”’, and I have no doubt if they could
454 W. Rh. Jones—Tin-mining at Ulw Bakau, F.M.S.
distinguish topaz from quartz they would know the former mineral also by a name signifying intimate relationship with cassiterite.
The rock is phenomenally rich in tin-ore, and typical specimens were collected and found to contain 23-9 per cent of cassiterite. The extraordinary enrichment occurs at the intersection of two main lodes and one subsidiary lode.
The mine is worked on 55 per cent tribute, with the result that only the very rich ‘lode-stuff’ is crushed, and attention is given, not to the ultimate economic development of the mine, but to the recovery of as much tin-ore as possible before a certain date.
Granite containing from five to six times the percentage of ore profitably worked in Cornwall is at present being thrown on the dump-heap, but under the circumstances this is justifiable, and as the dump-heap will eventually be worked there is no ultimate waste of the country’s mineral resources. Water is very scarce, and the rock, after being crushed by foot-stamps, accumulates more rapidly than it can be treated. A heavy shower of rain enables the aceumu- lation to be washed, and so the work goes on.
‘« Bibby’s Lode.”’—This mine is also situated at Ulu Bakau, but is on the Pahang side of the main watershed. ‘The tin-ore is obtained from the undecomposed rock, and it is interesting to note that there are distinct differences in its character in different parts of the mine. These differences illustrate in a striking and conclusive manner the well-known theory of ‘‘ Differentiation of Granite”, and it will be helpful for the economic development of the mine to bear in mind
that the differences in the rock are more apparent than real; that .
what seems to be a totally different kind of rock is only a modified form of its neighbour. The whole of Ulu Bakau and the neighbour- hood is formed of granite. and its modifications, viz. pegmatites, aplites, quartz veins, and topazized granite or greisen. The latter rock is extremely interesting as evidence of great mineralization, for the accepted theory of its origin is that it is formed by the action of fluoriferous vapours on the felspar of the granite. ‘lhe presence of such a fluoride mineral is an indication, not only of mineralization, but also of tin-ore, which originally came up as the vapour of tin- fluoride. In this particular instance the topazized granite itself contains cassiterite. Good washes were obtained from such a rock on 4 mining lease about a mile along the path from Ulu Bakau. So far no work has been done on this spot.
Some of the mining engineers who have prospected this property have to some extent agreed that the hill has one wide horizontal lode running through it and six smaller lodes, also parallel, which run through part of the hill. The views they have gathered after careful work extending over some months are worthy of serious consideration, but the “following observations will, I believe, offer another solution to an extremely 1 interesting problem.
1. A main horizontal lode with other smaller parallel lodes running through a considerable hill would be a remarkable occurrence any- where; and in a district where faulting and thrusting have occurred on a tremendous scale it would be an extraordinary although not impossible disposition of the lodes, but in a hill which itself shows distinct faulting and thrusting it would be impossible.
a 2
W. R. Jones—Tin-mining at Ulu Bakawu, FMS. 455
_ 2. The bands of tin-ore-bearing rock cannot be taken as evidence of parallel lodes, for (1) the intervening rock has not been prospected except in a few places on the surface; (2) the actual outcrop of bands of rocks of the same strike would all appear as parallel out- crops ona hillside, no matter how great the variation in dip may be.
3. It is proved that the dip of this main lode varies from 15° in one direction to 5° in the opposite direction. The simplest explanation of such a variation in a faulted igneous rock is a fault, and such - faulting is clearly shown in photographs.
4. What is supposed to be the most convincing argument in favour of the horizontal lode theory is the horizontal upper surface of the tin-bearing ground shown in photographs.’
It will. be noticed, however, that the character of the rock shown above this horizontal surface is totally different from the underlying rock, and not only is it a much less acid type of granite but it is decomposed and contains granite boulders. The junction of the unweathered and weathered granite is remarkably sharp and well defined, and further evidence is at hand in the adjacent cutting in the same hill, on the same level, and within a hundred yards of the previous exposure. _
The faulting and thrusting caused a landslip which brought down the soil from higher up the mountain, smoothed the surface of the rock, and gave it the polished surface which it still possesses. Such landslips are common even to this day, and two fresh examples. on Gunong Raja can be seen from Ulu Bakau. "
This explanation also accounts for the disturbed and broken character of the rock between the fault and thrust planes and, whatis quite interesting, accounts for the formation of the steep valley immediately below where the rock, broken and crushed by the movement, was easily transported by water, leaving the more compact rock to form the steep sides of the valley. Such a case also occurs at Gunong Raja, ‘where one side of the valley is a huge polished perpendicular wall.
5. Numerous other pieces of evidence against the horizontal lode theory could be pointed out on the ground, but perhaps sufficient evidence has been given to show that it would be utterly unsafe to attempt a calculation of the amount of tin-bearing rock in this hill with the facts now available.
The question can, however, be approached in another and safer way, and one which will furnish the Government with a better conception of the amount of tin-bearing rock in this part of Ulu Bakau.
Very strong mineralization is to be seen on Messrs. Bibby & Ruxton’s property over an extensive area, but in parts the rock is barren of tin- ore. ‘he barren areas are considerable, and the amount of non- payable cassiterite-bearing rock is also extensive. ‘There is on this property, however, sufficient proved ground to give the mine a life for many years, and there is every indication of mineralization extending right into the mountain and into the adjoining land on
1 The junction is between a quartz-topaz vein and porphyritic granite.— J.B.S.
56h eR: Horwood—Upper Trias, Lewestershire.
the Selangor side of the watershed, the one leased by Towkay T. Kim Bee.
~The few adits driven into the mountain-side on the Selangor boundary show the presence of the tin-ore-bearing rock now being profitably exploited on the Pahang side, namely, a fine-grained to saccharoidal topazized granite or greisen passing into a quartz rock containing only a little topaz, and in some places into quartz free’ from topaz. ‘The cassiterite is disseminated through the rock. The picked material crushed by foot-stamps was found to contain 6°8 per cent of tin-ore, and in another place 4:2 per cent, whereas the rock crushed at the mill varied from 1 to 2 per cent. These figures were obtained from specimens collected on my visit, but considerable variation occurs daily, although the average from the whole mine may be fairly constant.
The mineralization in this neighbourhood is so general and extensive that it is safe to predict for tin-mining a life of several years, if, of course, the metal remains at a good price.
About 60 chains to the south-east of the Trigonometrical beacon of Ulu Bakau is a mine now being worked by lampanning. A vein of cassiterite-bearing rock has been exposed fora distance of 61 feet, having a direction of 81° south of east. The Chinese knew that this contained tin-ore and were enthusiastic over it, but confined their attention to lampanning for the present. There is considerable amount of lampanning to be done, but the tailings will not, fortunately, cover up the exposed veins.—W. R. J.
GEOLOGIST’S OFFICE, BATU GAJAH, F.M.S.
September 23, 1913.
VI.—Tue Urrrr Trias oF LEICESTERSHIRE. (Continued from the September Number, p. 422.) By A. R. Horwoop, F.L.S.
8. Economics anD WaTER SUPPLY.
[{\HE economic resources of the Trias as a whole are not eran if we
exclude the two main industries (bricks and gypsum), but.they are of interest from a practical standpoint, so that a short summary will be given here.
The great impetus given to the quarrying of granite, syenite, and allied igneous rocks by improvements in blasting and boring methods has more or less caused the industry in Triassic building stones to become obsolete.
At one time thick-bedded sandstones were used for building stone at Kegworth and other places in that district, and they were formerly worked at Burton, Bretby, Castle Donington, Donington Park, Weston near Ashby, and at Warton, just outside this area;. but they are rather soft, though hardening on exposure, and sometimes cemented by barium sulphate. They are worked at Melbourne and Weston.
In the Upper Keuper’ the Dane Hill Sandstone series has been |
1 Locally some thick-bedded skerries have been utilized in some cases.
A. R. Horwood— Upper Trias, Lewestershire. 457
worked at Dane Hill, where old quarries still exist. Many of the Roman architectural remains in the Leicester Museum testify to its use in Roman buildings. It hardens on exposure, but is friable and soft. The Orton-on-the-Hill Sandstone group’ has been used for building at Diseworth and Kegworth, and probably at Orton, but no quarries now exist.
Building sand is obtained from the Lower Keuper near Atherstone, and it is used for the same purpose at Leicester, the Upper Keuper Dane Hill Sandstone being utilized. Where of a sandy character the Upper Keuper marls are used for sand at Leicester. The marls of the Lower Keuper are used for brick-making at Coalville, Ellistown, Ibstock, Heather, Measham, and about Atherstone, as well as in the Nottingham and Derby district.
In the Red Marl area brick-making is carried on extensively, being the main industry, close to the principal towns and lines of railway. Some forms, with much lime and skerry, are unsuitable for this, but the higher beds as a rule yield a good form of brick-clay, and the local glacial clays when free from stones are sometimes mixed with them, as at Sileby and near Leicester. Pits are at work at Hathern, Loughborough, Sileby, Belgrave, Thurmaston, Knighton, Blaby, Glenfield, Bagworth, Ashby, Waterloo Hill, Burton, Quorn, Hoton, Walton, and elsewhere.
The Tea-green Marls have been utilized for brick-making at Glen Parva and Gipsy Lane, and formerly at Spinney Hills, and in the Rhetic beds of that place and at Glen Parva, but the last-named pit is now filled with water.
Road-metal was obtained from the Orton Hill Sandstone at
Diseworth, and the flinty limestones of the Upper Rhetics have been used in South Notts. The Rhetic limestones and nodular limestones of the Tea-green Marls figure as tessere in the local Roman pavements.
Gypsum locally is not of such importance as at Newark and elsewhere in Notts. In this area it is worked at Gotham, Thrumpton, Kingston, and West Leake, where it is ground for plaster. Near Leicester the only use to which it is put is for grotto work, and it can be obtained for 5s. a cartload. Some ornamental work was formerly executed in the district, however, as the alabaster font at Old Humber- stone Church was made from the Gipsy Lane mineral. Plaster is only made to a limited extent at Leicester. It was formerly mined at an old pit on the Regent Road. ‘Toa slight extent it is used as a top dressing for soils,” but since the introduction of artificial manures the practice has been largely discontinued. The fibrous gypsum or satin’ spar from which ornaments are made is of as good quality and some- times nearly as thick as in Notts, where it sold for £6 to £7 a ton at one time and was sent to Derby, where it was made into brooches, bracelets, etc., and shipped abroad. Formerly the alabaster industry must have been carried on locally, as many ecclesiastical monuments
1 The stone was used for threshing-floors at Orton, Austrey, Copt Oak, Charley, where bricks were also made. 2 Fetching at one time 10s. a ton.
458 A. R. Horwood—Upper Trias, Leicestershire.
and ornaments exist in the churches of Leicestershire, and it is improbable that they all came from Tutbury, where it was largely worked years ago, and where mural tablets, etc., were made. In Tutbury Church are tombs dedicated to Henry de Ferrers and Sir John de Hanbury, and ornament of Norman age adorns’ the pillars, whilst alabaster tombs at Norbury, Ashbourne, Newton Sulney, Burton (knight temp. Edward III), and elsewhere were made
from the Tutbury rock. During the fourteenth century up to the -
Commonwealth period alabaster was an important industry at Burton.
Chellaston now takes the place of Tutbury and Fauld. At the former the gypsum is 14 feet thick, and is sent to Derby, Buxton, and the Potteries, a large amount of plaster of Paris being used in modelling and as an imitation marble in Scagliola. It is used for obtaining copies of sculptures, medals, gems, and a variety of other things of which a replica is required, figuring largely in museums, for moulds, for electro work, stereotyping, glasswork, cornices, plastered ceilings, panels, pilasters, etc. The large tazza at the Museum of Practical Geology came from Fauld, where slabs 9-10 feet are manipulated.
Another use for gypsum is for Burtonizing beer. In the Burton beers some 850,000 lb. of gypsum are annually consumed. A similar ' water is utilized for brewing at Newark, the proportion of sulphuric acid being over 65 per cent, in the Burton waters 57 per cent. The Leicester breweries are supplied with water which also contains much sulphate of lime diluted down to 40 grains per gallon from 100.
The soils of the Lower Keuper are loamy and retentive, but friable and suitable for arable, that is, the marls, which give a red loam, which is equally adapted to arable, grass, or orchards, and market gardens, as seen in the Mease Valley.
The Upper Keuper Marls form good cornland, but require subsoil drainage. The percentage of silica is over 50, alumina 15, lime 3-4, magnesia 5, potash 4, and carbonic acid 4 per cent. Where the subsoil is sandy a loamy soil results. This is modified by the oceur- rence of skerries and mixture with drift, often, as around Melton, pebbly. It forms good pasture, being stiff and clayey, and like most
red beds is excellent for fruit-trees. Trees grow well upon the
sandstone horizons.
The Tea-green Marls form only a narrow band and are less siliceous and more calcareous than the Red Marls in this respect, approaching the Rhetic beds, which contain more carbonie acid (20 per cent) and more lime.
The Bone-bed, which in some districts contain phosphatic nodules, yielding manure, is here only a gritty or pebbly sandstone. There is no trace of a bone-bed in the Tea-green Marl, such as that at Gold Cliff, but paleontologically it is represented by a series of definite bands with fish-scales. Some of the marly limestones are practically similar to Fuller’s Earth, and a clay at the base of the Tea-green Marl has been worked at Emborrow, Somerset.
Economically the Red Marl has been classed with Chalk Marl, Fuller’s Earth, Kimeridge Clay, Gault Clay, and London Clay, all
—
A. Rk. Horwood—Upper Trias, Levestershire. 459
highly fertile formations, and the red beds have been characterized as the most fertile landin England. The red colour which is indicated by the name Ratcliffe, Red Hill, is retentive to the rays of the sun in marked contrast to the blue clays of the Lias, which are not suited to arable land as a rule, thus differing from the Marlstone, which yields also a red and fertile soil (cf. Rutland).
Thus, in so far as Leicestershire is concerned, the Upper Trias constitutes the richest part of the county, apart from the mineral products, the Middle Lias (if we exclude the syenite and Barrow limestone and coal industry) coming next in respect of the soil fertility and mineral resources. There is so little Oolite in the county that its much higher relative soil value need not be taken into account.
The main source of water ‘supply from the Upper Trias is the Lower Keuper Sandstone, called Waterstones. This name, however, is unfortunate, for it really applies to the character that the marls possess in regard to texture, resembling the appearance of watered silk,’ which is well shown in the sections at Appleby. At the present time the supply of water from the Trias is not generally utilized, the larger towns, such as Loughborough and Leicester, receiving their water from Charnian reservoirs or from the upper reaches of the Derwent, largely derived from Millstone Grit and older Paleozoic rocks. Formerly many small villages received their supply from the Lower Keuper, and the distribution of -villages along the outcrop indicates the importance of this formation at one time as a water- bearing stratum. Its abundance at certain horizons is shown by the following borings. At Newtown Unthank water overflowed the top ‘of the borehole, sunk to a depth of 615 feet, the Waterstones being 120 feet thick, Coal-measures 353 feet, water being met with first at a depth of 220 feet.
At Hathern a boring was made to a depth of 320 feet below - 140 feet of Lower Keuper Sandstones into conglomerates, and water was abundant. At Chilwell water rose to the top of the boring, 435 it. 9in., from below Waterstones 115 feet, with Bunter and Permian beds beneath.
At the Spinney Hill boring water was met with in a boring of 600 feet (increased later) at 400 feet in Waterstones (232 feet), or more probably Red Marl. At Lindridge water overflowed the top of the borehole (270 feet) when Waterstones were reached. At Elmesthorpe it was found to be constant at 800feet in a boring 1,440 feet, the Waterstones being 330 feet and the Coal-measures 980 feet thick Ina boring at Hinckley, one mile W.N.W., made November, 1877, the water rose to 237 feet from the surface in a boring 805 feet deep from Waterstones. There were 530 grains of solids and 39 grains of chlorine in the imperial gallon, and the yield was 400,000 gallons per day. The same feature was noticed
1 The marls are impervious and dry, the sandstones pervious, 60,000 gallons per hour being obtained from waterstones at Hllistown at a depth of 300 feet, and at a depth of 670 feet in another boring pure limpid water rose 40 feet above the borehole.
460 <A. R. Horwood—Upper Trias, Leicestershire.
in borings at South Scarle, where water rose from 1,500 feet to 5 feet above the top of the borehole, and at Retford, where it rose to within 6 feet of the surface from a depth of 600feet. At Ibstock at a depth of 108 feet the supply of water was 6, 8, and 9 gallons a minute, at Bagworth from conglomerate 600 gallons per hour at a depth of 299ft. 4in. At Snarestone 80 gallons per minute were registered at 51 feet, 100 gallons per minute at 99 feet (from a marl parting below pebbles), and 200 gallons per minute at 109ft. 3in. The water is thus abundant and permanent. It is not so hard as that from the Upper Keuper Red Marl (always scarce) and sandstones. The water percolates along the outcrop along the line of dip, and is prevented from escaping by the intercalated marls, so that artesian wells are suitable for securing a supply from it.
Little water is derived from the Red Marl, and such as it is is too hard for potable purposes, though, as has been mentioned, it is excellent for Burtonizing beer. Where sandstone bands or skerries are intercalated with it and gypsum beds, however, a certain supply is obtainable. Some of these sandstones outcropping on hillsides take up water in. the same way as the Lower Keuper, and it flows down the dip, but the supply is limited, as is also the supply from the gypsum bands.
At Burton an analysis of water obtained from an artesian well at a depth of 70 feet, used for brewing, was as follows :—
Grains in Imperial
Gallon.
Sulphate of lime ! : 5 j 3 : 70-994 Carbonate of lime . : a c . é 9-046 Carbonate of magnesia a : : : 5-880 Sulphate of magnesia : ‘ : : : 12-600 Sulphate of soda : : f : : . 13-300 Chloride of sodium . : : : : : 9-170 Chloride of potassium ; ; 4 : : -966 Carbonate of protoxide of iron . 6 , fj 1-218 Silica ; : . : ; : : , 1-120
Total solid residue . : . 124-294
In water obtained from a boring for water at Hinckley, where it stood at 630-80 feet, the depth being 705 ft. 2in., there was a considerable amount of solid salts, and the salt spring or holy well owed its reputation to the same cause. The average analysis was :—
Per 100,000 Gallons. Lime A b ; ; ; i 4 ; 67-31 Soda i x é 4 ; : , x 202-50 Magnesia . : : 3 : i 5 : 19-00 Sulphuric acid . ‘ : s ; é ‘ 295-60 Carbonic acid . : : : é ; i 16-67 Silicie acid 3 ’ : : : : ‘ 2-00 Chlorine . , 5 : : , A h 61-70
664-78
A. R. Horwood—Upper Trias, Leicestershire. 461
It was combined thus :—
Per 100,000 Gallons. Sodium chloride : ! 6 s , : 101-67 Sodium sulphate : : ; : : : 340-39 Calcium sulphate : : ; : : : 163-47 Magnesium sulphate . 4 i 4 : , 11-50 Magnesium carbonate ! 5 : : ‘ 31-85 Silicic acid es : ‘ 3 : : i 2-00 650-88 Add oxygen equal to chlorine . ; ; : 13-90 664-78
The specific gravity was 1:0060. In 100,000 gallons there were 98 1b. of sulphate and carbonate of lime and 23 lb. of chlorine gas. This compares well with the water which is used at Leamington Spa and Shearsby Spa in Leicestershire. It was limpid and clear, but brackish. By pumping the solids were reduced from 650 to 465. A similar water was met with at Bates’s Brewery at 30 feet, containing 100 grains to the gallon.
In a boring at Ansty Paper Mill no water was met with below the gypsum. But in other cases wells 30-80 feet deep tapped an abundant supply, and water in one case burst through as soon as the gypsum was pierced, though marls above and below were dry. At Bagworth 7,200 gallons per hour were met with under gypsum at a depth of 197 feet, 100 gallons a minute at Desford at 109 ft. 8 in. (hardness
- 130°), and in South Leicestershire 17 gallons a minute.
The Upper Keuper Sandstone supply is not abundant and is hard.
At Croft water issued constantly from a fissure at the bottom of a deep cutting, running constantly for eight months. A pump - connected with a boring 130 feet deep yielded 100,000 gallons in ten hours, but the water was in this case very soft. Many wells in Leicester formerly derived a supply from this level up to 250,000 to 300,000 gallons per day. Thus, a well in Bond Street (Messrs. Fielding Johnson), sunk 151 feet, had water standing at 20 feet from the top, and similar wells were sunk in London Road by Messrs. Davis, and in Wharf Street by Messrs. Raven. In Churchgate (Messrs. Gimson) a well 70 feet deep had water standing at 55 feet from the bottom, and at St. Margaret’s Works (Messrs. Corah) a well 84 feet had water at 72 feet from Upper Keuper Sandstones (26 feet thick).
No water is derived from the Tea-green Marls or Rheties. Wells sunk to the latter have failed to meet with water. There is also too much iron pyrites in the latter to make the water palatable, except for mineral use.
The well-known Shearsby Spa deriyes its water from Keuper beds overlaid by Lias clays, etc. (perhaps 700 feet thick). It is very saline, brackish, but not acid. It has the smell of rotten eggs characteristic of sulphuretted hydrogen, and was used (in baths) for scorbutic diseases. It resembles the waters of Leamington,
462 I. C. Chacko—On Cordierite.
Cheltenham, and Rugby. The specific gravity is 1:00469. It contains in an imperial gallon—
Carbonate ofiron . - i 3 3 5 traces Carbonate of lime . ‘ é : : ‘ 9-743 grains Carbonate of magnesia . 2 ‘ 4 2 6-246 ,, Carbonate of soda . : é : : : 5-582 25; Sulphate ofsoda . . ; ! Y x 128-989 ,, Chloride of sodium . i : : k ; 245-532 —y, Chloride of potassium : ; : ‘ ; traces Hydrosulphide of sodium i 4 4 : AHI BY | nn Iodine and bromine combined . : 2 : traces 396-366
The Old Spa on Humberstone Road, near the Wesleyan Chapel,
derived its reputation from similar Triassic waters. Formerly there were salt springs at Weston, near Ingestre in Staffordshire, and brine at Branstone, near Burton, but there is no brine in the Leicestershire Trias.
The brine springs at Moira are thought to have derived their supply from Triassic beds overlying them. The Ashby baths were long noted for the waters procured from this source, and used for rheumatism, etc. In this water there is more bromine than in most Triassic waters, the springs at Cheltenham yielding 38°65 grains per gallon. The Moira brine contains per imperial gallon :—
Grains. Bromide of potassium and magnesium d 0 8-0 Chloride of sodium . : : A : 5 3700: Chloride of calcium . ; : : . : 851-2 Chloride of magnesium . ; : : 5 16-0 Chloride of potassium c ‘ : : : “0 Iron as protochloride . : : : : 5 trace 4575-7
(To be continued.)
VII.—Opricatty Posrrrve CorDIERITE.
By I. C. Cuacxo, B.Sc. (Lond.), B.A., A.R.S.M., A.B.C.S. (Lond.), State Geologist, Trivandrum, Government of Travancore, South India. NORDIERITE was first found in Travancore at Teruwulla (lat. () 9° 22’ N. and long. 76° 37’ KE.) in a kind of diorite. In the hand-specimen the mineral appears as violet patches and spots.
Monazite, magnetite or ilmenite, garnet and biotite with probably a little hornblende, occur in association with it. In the sections the
mineral is found to contain numerous globular inclusions which are surrounded by pleochroic halos. The larger of these may be identified as monazite under the microscope. The mineral is itself pleochroic, light vibrating in the direction of the axis of mean velocity (Y) showing a pronounced violet tint. When light vibrates in other directions the plates do not show any distinct colour, but a faint yellow tint may be observed in some plates. When light vibrates in the direction of the Y axis the pleochroic halos round the inclusions disappear and assume the violet tint of the crystal plate. Cordierite is supposed to occur usually in metamorphosed sediments, and the pleochroic halos are regarded as due to the presence of
I. 0. Chacko—On Cordierite. 463
organic impurities. Buta sedimentary origin is out of the question in the present case. It is held by some that pleochroic halos are due to the presence of radio-active substances. I kept an Ilford Empress photographic plate exposed in a dark box to a crushed sample of the mineral for more than twelve hours, but on development the plate did not show any indication of having been affected by the mineral.
Lamellar twinning is very common. But for its pleochroism the mineral may be mistaken for plagioclase on account of the similarity of its twinning and refractive index to those of felspar.
Cordierite is usually negative in optical character. But I think at least some of the crystals are optically positive in the present case. The optical character of a mineral is not an absolutely invariable property of it, especially when the axial angle lies in the neigh- bourhood of 90°. When the angle is nearly 90°, a slight variation in it may change the character of a mineral from negative to positive or from positive to negative. Slight variations, and in some cases large variations, in the axial angles of minerals are very common. In the case of cordierite the axial angle is very nearly 90°, and _ a change in optical character may be expected. At the same time it must be remembered that the very fact that the angle is nearly 90° makes it difficult to distinguish the acute bisectrix from the obtuse with an ordinary petrological microscope, and on this account there is possibility of error in the observations. Minerals of double optical character are not, however, unknown. Among biaxial minerals, anthophyllite, penninite, and kammererite are examples.
Owing to the presence of inclusions and the intimate association of the mineral with other minerals, it is not easy to determine its density with accuracy. Ina series of separations of a finely crushed sample with Klein’s solution, particles of the violet mineral were found to sink at various stages of the density of the solution between 3°00 and 2°60 approximately. The denser particles are regarded as having inclusions or as associated with other heavy minerals. For the analysis given below such particles of the violet mineral as floated in a heavy solution in which a quartz crystal would just sink were selected. An analysis of such selected grains of the cordierite gave the following results :—
Water. é : ‘ 4 4 : 1-74 Silica j 4 : , H M . 49-74 Ferric oxide . ; x 4 ‘ : 5-65 Ferrous oxide . ‘ K 4 - : 3-00 Alumina . ; 4 : i J uno Lime , 5 ; ‘ : ‘ 3 1-05 Magnesia : : : : : 4 4-30
100-69
What strikes one first in this analysis is the high percentage of ferric oxide. Of the eleven analyses given by Dana of samples of cordierite from various localities, nine do not give any ferric oxide at all, while two give only 0°63 and 0°38 per cent of ferric oxide respectively. On the other hand, the percentage of ferrous oxide is low in the present analysis. Magnesium replacing ferrous iron in
464 Notices of Memoirs—British Association.
cordierite, a decrease in the latter is to be accompanied with an increase in the former. Inthe present case the percentage of magnesia is also low. ‘The ferrous equivalent of the sum of ferrous oxide and magnesia does not fall below 22 per cent in the analyses given by Dana, while it is as high as 27 per cent in the case of Finland cordierite. The percentage of alumina usually does not go beyond 83, whereas in the present case it is as high as 35:2. The other constituents remain within normal limits. If we may rely on the accuracy of this analysis, this cordierite is of a peculiar constitution. It must, however, be remembered that there is just a possibility of error in the determination of the two oxides of iron.
The positive character of some of these cordierite crystals is confirmed by the observations of Mr. G. dep. Cotter, Assistant Super- intendent, Geological Survey of India. His remarks on the mineral are given below :—
‘‘In the slide which Mr. Chacko now sends I find that one section of cordierite gives a positive figure and one section gives a negative figure. I have also found a positive figure from the cordierite from Vizagapatam, 16/189. his is probably due to the increase of the — value of 2V beyond 90° (see Iddings). 2V in cordierite is very variable, and the lower the refractive the greater is 2V. The mineral sent now by Mr. Chacko has been tested by the method of Schroeder Van der Kohlk, and its refractive index lies between nitro- benzene and cedar oil, and it gives reds and blues for a mixture of both. Therefore its refractive index is about 1:53, that is, fairly low. We may then conclude that 2V is probably large. In fact, T agree with what Mr. Chacko suggests, and think it might be worth publishing if he cares to do so. There is no section in the slide suited to the actual measurement of 2V.”
NOTICHS OF MEMOIRS.
I.—BritisH AssocraTION FOR THE ADVANCEMENT OF Science, Erenty- sixtH AnnuAL Mertine, NewcastLe-upon-Tynb, SePrEMBER 6-8, 1916.
List or AuTHoRS AND TITLES oF PAPERS READ IN SECTION C (Gxotoax).
Presidential Address by Professor W. S. Boulton.
Professor G. A. Lebour.—Address on the Local Geology.
Dr. D. Woolacott.—Some Notes on the Permian of Durham.
Dr. @. Hickling. —Underground Contours of the Black Mine.
Professor W. G. Fearnsides. —Underground Contours of the Barnsley Mine.
Joint Meeting with Section E in the Room of Section OC.
Dr. A. Wilmore.—The Physical Geography and Geology of the Northern Pennines.
Professor W. G. Fearnsides and Dr. P. G. H. Boswell.—Note on the Occurrence of Refractory Sands and Associated Materials occurring in Hollows in the Surface of the Mountain Limestone District of Derbyshire and Staffordshire.
Dr. P. G. H. Boswell.—Geological Characters of Sands used in Re. Manufacture.
Papers on Geology. 465
Reports of Research Committees :—
Dr. W. T. Gordon.—Report of Committee to investigate the Flora of Lower Carboniferous times as exemplified at a newly discovered locality at Gullane, Haddingtonshire.
Professor T. Johnston.—The Old Red Sandstone Rocks of Kiltorcan, Ireland. |
Dr. W. Mackve and Dr. J. Horne.—Report of Committee to excavate Critical Sections in Old Red Sandstone Rocks at MRhynie, Aberdeenshire.
Dr. R. Kidston, F.R.S. and Professor W. H. Lang, F.R.S.— Description of a new fossil plant, Rhynia Gwynne-vaughant found at Rhynie.
Joint Meeting with Section B in the Room of Section C.—On the investigation of the chemical and geological characters of different varieties of coal, with a view to their most effective utilization as fuel, and to the extraction of by-products.
Discussion opened by Professor G. A. Lebour; and followed by Professor W. A. Bone, F.R.S., Dr. A. Strahan, F.R.S., Dr. J. T. Dunn, and others.
Mr. Joseph Lomax.—Microscopical Examination of Coal as a means of Identification and Correlation of Seams.
Mr. Leonard Hawkes.—The Acid Rocks of Iceland.
Dr. Alexander Scott.—The Petrology of the Arran Pitchstones.
Dr. J. W. Hvans.—Methods of representing Geological Formations and Structures in black and white on Maps.
Mr. Leonard Hawkes.—The Acid Rocks of Iceland.
Dr. Alexander Scott.—The Petrology of the Arran Pitchstones.
LE. Heron-Allen.—The Application of X-rays to the Determination of the internal Structure of Microscopic Fossils, especially with regard to the Dimorphism of the Nummulites.
Professor W. W. Watts, F.R.S.—Geological Photographs.
- PAPERS READ IN OTHER SEcrIons BEARING ON GEOLOGY.
Szcrion D.—Zooxnoer.
Professor A. Meek.—The Scales of Fishes and their value! as an aid to investigation.
Srction E.—GrocraPny.
aes eruce The Weddell Sea:
Suction H.—ANnTHROPOLOGY.
Professor W. J. Sollas, F.R.S.—A Sub-Crag Flint Implement. Dr. Marrett.—Recent Archeological Discoveries in the Channel Islands. .
Secrion K.—Borany.
Joint Meeting with Section C in the Rooms of Section K (Botany).
Discussion on the bearing of Botanical Science on Coal, to be opened by Dr. Marie C. Stopes.
Professor Rk. H. Yapp.—The Origin of Salt-marsh Pans.
DECADE VI.—VOL. III.—NO. X. 30
466 Notices of Memoirs—Dr. Boswell—Glass Sands.
Discussion on the Utilization of Waste Lands, introduced by Professor F. W. Oliver, and including the following short papers :—
P. A. Martineau.—The Afforestation of Pit Banks: Discussion.
Professor F-. W. Oliver.—Maritime Wastes.
Professor W. B. Bottomley.— Waste Moorlands.
Professor J. Lloyd Williams.—Reclamation of Peaty Soils in ‘Carnarvonshire.
Dr. W. &. Smith.—Utilization of Northern Mountain and Heath Land.
Il.— Some GrotogicAaL CHARACTERS OF SANDS USED IN GLASS Manouracrure. By P. G. H. Boswetr, A.R.C.Sc., D.Se., F.G.S.
T a time when it is necessary to know the extent and value of A our national resources of sands suitable for various industrial purposes, including glass manufacture, it is especially desirable that we should realize the particular properties of such sands and the geological conditions under which the deposits occur in the field.
1. In chemical composition, for all general purposes of glass- making, the sand should contain a very high proportion of silica, if possible over 99 per cent. ‘he percentage of iron (estimated at Fe, O,) should be as low as possible, For optical glass, table-ware (‘crystal’), etc., it should not rise above 0°5 percent; for laboratory- ware, globes, aud all second-grade glass-ware, a percentage up to 0-02 is permissible; for plate and window-glass and good white bottle-glass, the proportion may reach 0°3 or 0:4 per cent; and for rough bottle-glass and other similar work, a limit of 2 per cent may beadmitted. For refractory glass, such as that used for thermometers, gauges, certain laboratory-ware, etc., it is an advantage to find a sand bearing 4 per cent or more of alumina. Unfortunately, most British sands bearing alumina carry also iron and other undesirable impurities. Other bases such as lime, magnesia, titanium, and alkalies, should, if present at all, exist only in negligible quantities. In the analyses the loss on ignition should also appear; it yields an indication of the amount of water and organic substances present. The latter are not objectionable as they usually ‘burn out’.
The analysis of one of the best British glass-sands, a sample of Lower Greensand from Aylesbury, indicates $iO,, 99°80 per cent ; Al, O3, 0°32 per cent; Feg Og, 0°03 percent; loss on ignition, 0°22 per cent; total, 100°37 per cent. With this may be compared a well-known German glass-sand from Lippe: 810g, 99°88 per cent; . Aly Og, 0°18 per cent; Fes O3, 0°02 per cent; loss on ignition, 0°21 per cent; total, 100-29 per cent.
2. ¥or all but the highest quality glass, where the cost of crushing the raw material to a fine even state, with suitable subsequent treatment, is not prohibitive, the mechanical composition is of the utmost importance. The sand used should, if possible, be perfectly eraded, that is, it should be composed of grains all of the same size. Such perfection of grading is not attained as a result of natural agencies; the best-graded natural deposits contain over 90 per cent of grains of one grade, which, for glass-making purposes, is preferably
Notices of Memoirs—Dr. Boswell—Glass Sands. 467
the medium-sand grade (diameter >4 and<imm.). A high percentage of the fine-sand grade (diameter >and <;mm.) would be even more preferable, but suitable sands with a high proportion of this grade are not of common occurrence in this country. Coarser sand- grains are not desirable, and, if present, should be removed by sieving. Very fine sand, silt, and clay-grades are inimical, and must be removed by washing.
3. The mineral composition should be as simpie as possible, contain only quartz, or quartz and felspar, and the heavy detrital minerals present should be small in quantity and simple in com- position.
The treatment of sands (whether chemical, to remove iron, or mechanical, to ensure good grading) often involves prohibitive expense. It is therefore of considerable importance to look into the geological conditions under which desirable glass-sands occur. We may thus receive clues to the existence of further supplies by knowing the kind of deposits in which they are met, and the special conditions under which we may expect to find them. The important supplies of glass-sands occurring in Western Europe are associated with rafts of braunkohle in beds of Miocene age; Hohenboka sand, of the same age, containing carbonaceous layers; Fontainebleau sand, in Upper Oligocene deposits, with lignites; Inferior Oolite sands in the Yorkshire and Northampton districts, containing planty matter and roots; Berrythorpe sand (Callovian), containing carbonized woody material and peaty matter; Aylesbury and Leighton Buzzard sands (Lower Greensand) with peaty bands; Headon Hill and Bagshot. from Alum Bay, Wareham, and other places (Hocene, etc.), inter- bedded with lgnites. Numerous other examples may be adduced. Attention also may be drawn to the very pure sandstones of the Coal-measures, associated with coal-seams, and to the white sandstones found with the Brora coals of Scotland (Callovian). The bleaching ‘of the reddish sands, for a foot or two in depth, upon our heaths, is a similar phenomenon. In each case the freedom from iron may be attributed to the reducing action of the planty matter, in changing the ferric salts to the more soluble ferrous state, when they are more easily removed by percolating waters.
The beds of white sand seem always to be of limited thickness, and frequently to be laid down under lagoon or estuarine conditions favouring the development of plant life. Cementation is objectionable, either because of the introduction of impurities or because of the cost of subsequent crushing. It is desirable, therefore, that the deposits should be incoherent. The most widely used sands are thus those of comparatively late geological age. Most of them occur in Tertiary deposits, but some are Cretaceous in age. A _ strong tendency, also, exists for the simplification in mineral constitution (due to elimination of more easily decomposable minerals) and greater perfection of grading in the later geological sediments—a result of their constituents having passed through many geological cycles.
[This, and the two following Notices, are Abstracts of papers read in Section C (Geology), British Association, Newcastle-on-Tyne, September, 1916. ]
468 Notices of Memoirs—L. Hawkes—Rocks of Iceland.
IlI.—Tur Acm Rocxs or Iceranp. By Lronarp Hawxes, M.Sc.
N account was given of the preliminary results of an investigation of the Tertiary Acid series. It is known that these rocks are widely developed in Kast Iceland, but hitherto definite information as to their extent, nature, and mode of occurrence has been lacking. Whilst they have been stated to be partly intrusive and partly extrusive,' it has generally been accepted that they are dominantly intrusive in character,” a view which has probably been influenced by the general intrusive nature of the British Tertiary acid rocks.°
The main exposures of acid rocks in East Iceland from Borganfjord to Bernfjord have been studied in the field. Evidence was brought forward to show that these rocks are in the main extrusive in character. In places the acid series is at least 2,000 feet in thickness. Tuffs and spherolitic liparites and obsidians are very common. The author holds that the old view, that the acid rocks are dominantly intrusive, being thus marked off from the basic rocks, is incorrect. Tertiary volcanic activity was similar to that which has obtained in Iceland in post-Glacial times, when acid rocks have been extruded . along with the basic, but in a smaller amount. Acid eruptions seem to have taken place almost continuously during the building up of the Tertiary plateau. The uneroded character of the liparite lava- streams shows how rapidly the successive basalts which submerge them were poured out, and this throws some light on the problem of the intrusive or extrusive origin of the Antrim rhyolites.
- Since the close of the Tertiary volcanic period enormous denudation has obtained, and the varying resistance offered to erosive agents by acid and basic rocks has produced some remarkable effects.
Thoroddsen has described some peculiar streams of acid rocks which he regards as post-Glacial lava-flows, formed by the extrusion of liparite blocks in a half-melted condition from the mountain sides. The most noteworthy of these occurs in the Lodmundarfjord. The rocks of the district are Tertiary bedded basalts with the exception of an acid series, contemporaneous with the basalts, revealed in a huge cirque excavation in aside valley. The valley is full ofa chaotic assemblage largely composed of spherolitic liparite reaching down from the cirque (Skimhottur) on the bottom of the main valley (Lodmundarfjord).
The author holds that these blocks do not represent a lava-stream but a moraine. All the rocks of the stream occur in situ in the Skimhéttur mountain. The theory of morainic origin has been previously rejected, partly on account of the reported exclusive liparite composition, where a mixture of acid and basie rocks would have been expected. It was found, however, that the stream is not exclusively composed of acid types, though dominantly so. ‘The
1 Th. Thoroddsen, ‘‘Island: Grundriss der Geographie und Geologie,”’ No. 152: Pet. Mitt., 1905, p. 269.
2 Ibid., p. 232. H. Pjeturss, ‘‘Island’’: Handbuch der Regionalen Geologie, 1910, p. 5. OC. W. Schmidt, ‘‘ Der Liparite Islands in geologischer und petrographischer Beziehung’’: Zeit. Deutsch. geol. Ges., vol. xxxvii, p. 783, 1885.
3 Sir A. Geikie, Ancient Volcanoes of Great Britain, vol. ii, p. 364, 1897.
Notices of Memorirs—Dr. Scott—The Arran Pitchstones. 469
large proportion of liparite present results from its lesser resistance to ice-erosion compared with basalt, whereby the huge cirque has been excavated where the acid rocks occur, and the material deposited to form the present remarkable stream. It has also been objected that none of the blocks are ice-scratched, but this is not to be expected owing to the exceptional fissility of liparite and its rapid degradation under weathering influences. The author has never seen an ice-scratched boulder in Iceland.
IV.—Tuer Perrotocy or THE ARRAN Pircusrones. By ALEXANDER Scorr, M.A., D.Sc.
LTHOUGH the Arran pitchstones are so widely known, no
extensive examination of them has ever been made. The
intrusions, which number about eighty, may be divided into the following groups :—
1. Non-porphyritic glasses with abundant riierolites which are generally hornblende. These are found chiefly in the district round the coast, and include the Corriegills and Monamore Glen occurrences.
2. Pitchstone porphyries with large phenocrysts of quartz and felspar and scarce augite, and with hornblende microlites. This group includes many of the dyke-rocks intrusive into the Goatfell granite.
_ 3. Pitchstone porphyries with aibans crete of felspar and pyroxene and subordinate quartz. The pyroxene includes both augite and enstatite, and scarce crystals of an iron-rich olivine also are found. - Microlites of pyroxene and of hornblende occur. This group is typical of the intrusions of the south end of the island.
4. More basic type with scarce phenocrysts and great abundance of pyroxene microlites. This group is represented by two occurrences in Glen Cloy and several around the great Tertiary volcanic vent.
Analyses have been made of each type, and the results show the existence of considerable variation in composition. An attempt has been made to determine the cooling histories from the examination of the field-relations and microscopic structures of the various types, and also to indicate the conditions which are responsible for such a large development of glassy intrusive rocks.
REVIEWS.
I.—Tup Larpr Staces or tHe Evoturion or tHE Jenrous Rocks. By N. L. Bowen. Journ. Geol., Supp. to vol. xxiii. pp. 91. 1915.
fY\HE determination of the processes whereby the various types of
igneous rock have been derived by differentiation from a few relatively simple magmas has long been, and still is, one of the chief problems of petrology. Of the hypotheses which have been advanced in order to explain differentiation, several have been discredited and are seldom advocated. nowadays; thus ‘‘Soret’s principle’’, to which
470 Reviews—N. L. Bowen—
attention was first called by Lagorio, has now been generally abandoned, mainly owing to the criticisms of Becker, Harker, and others. The theories still under discussion include those based on assimilation, pressure phenomena, the action of vapours, liquation, and fractional crystallization. Loewinson-Lessing held that the solution of foreign material was the chief factor, a view also held by Johnston-Lavis and, in a modified form, by Daly. The possible ‘influence of pressure has been indicated by Schweig, while Michel Lévy favoured the activity of the volatile constituents of the magma as the most potent operator in producing heterogeneity. The process of liquation, first advanced by Durocher, has received many supporters, including Daly, but fractional crystallization, as suggested by Becker, has also attracted much favour. In the paper under review this last hypothesis is advocated, the arguments being based on recent synthetic work on the equilibrium of mineral systems.
While in the earlier investigations the systems involved were simple, it has now been found possible to examine some, such as diopside -forsterite-silica, anorthite-forsterite-silica, and diopside- plagioclase, which approximate to certain simple types of igneous rocks. Bowen summarizes the information which has been obtained from these synthetic investigations, and bases on them a systematic theory of petrogenesis, with fractional crystallization, the sinking of crystals, and the squeezing out of the residual magma as the chief factors of differentiation. A basaltic magma is taken as the starting- point, and it is shown that the various ways in which this can crystallize may give rise to a sequence from granite to peridotite.
While the rapid cooling of such a magma produces a simple basalt, slow cooling, accompanied by the sinking of the early-formed crystals of pyroxene and lime-plagioclase, results in the enrichment of the upper liquid layers in alkali-felspar, and in their subsequent consolidation as diorite. With still slower cooling the residual material crystallizes as quartz-diorite, granodiorite, or granite. If the cooling history is such that the plagioclase crystals are zoned, the salic material may be found filling the interstices between the earlier minerals. If pyroxene alone separates out, the lower layers are composed of the ‘‘anchi-monomineralic”’ rock pyroxenite; if olivine alone sinks before resorption occurs, the resulting rock is dunite; if. pyroxene and olivine separate out together, or if the olivine is partly resorbed after sinking, various types of peridotite may be formed. The separation of these minerals which are poor in silica greatly enriches the upper layers in the latter oxide, which may, if the cooling has been sufficiently protracted, finally crystallize as
uartz.
Nevertheless, quartz is so abundant in igneous rocks that the early separation of olivine cannot alone be held responsible for its presence. The commonest ferromagnesian mineral in the acid rocks is biotite, and as this is relatively poor in silica Bowen holds that its early formation is responsible for the existence of much of the quartz. There is here a discrepancy between the synthetic work and the natural rocks, as the salic pole of the differentiation in the former is a pyroxene-bearing granite, and in the latter a biotite or hornblende
Evolution of Igneous Rocks. 471
granite. This is explained as ‘‘ the result of an increasing concentra- tion of the volatile constituents”, which lowers the temperature of consolidation and allows the formation of the water-bearing minerals, biotite and hornblende."
The origin of the alkaline rocks is traced to the influence of the water, fluorine, and other mineralizers. During the crystallization of biotite-granite, if the residual liquid be separated in some way from the already formed biotite and quartz, it must have a greatly increased concentration, not only of such volatile substances as H,O, Cl, $03, CO,, and so forth, but also of such alkali silicates as albite, orthoclase, nephelite, and kaliophilite; and the latter molecules may combine with the former to give the felspathoids. Thus the separation of the alkali-syenites may occur at any of the stages at which the formation of biotite and quartz is possible, that is, at any stage between diorite and granite. While this line of descent results from the maximum activity of the volatile constituents, there is an alternative which, in its earlier stages at least, represents the result of the minimum activity. If a gabbro magma be impoverished in water and similar constituents, the formation of biotite is inhibited, and the proportion of such silicates as orthoclase increased, so that the latter separates out along with lime-plagioclase, giving rise to an essexite or similar rock. Even in this case, however, the ultimate differentiate may be nephelite-syenite, if at any stage there is a concentration of the mineralizers. Thus we have the two alternate lines of descent of the alkaline rocks, the intermediate stages between gabbro and nephelite-syenite being, in the one case diorite and normal syenite, and in the other essexite and augite-syenite.
Leucite-bearing rocks are supposed to be formed in a similar fashion, and the fact that this comparatively rare mineral is practically confined to hypabyssal and effusive rocks is considered to be due to the facilities, which the latter often have, for the escape of -mineralizers, thus allowing the potassium salts to consolidate as leucite instead of the more complex minerals such as mica.
The fact that the theory has a sound experimental basis renders it less liable to criticism than most previous attempts. It must be remembered, however, that it is only the early stages, namely, the derivation of ultrabasic rocks on the one hand and of the diorite and certain syenites on the other, from the primary basaltic magma, that has been subjected to verification in the laboratory. Experimental difficulties have hitherto precluded any systematic investigation of water-bearing magmas, and hence comparatively little is known concerning the formation of the micas and other hydrated minerals. _ Recent work has demonstrated beyond all doubt the practical absence of eutectics in basaltic rocks, and has shown that the presence of solid solution between two or more of the constituents increases the variation in the possible results of the consolidation. Hence it is very unsafe to prophesy the results, of crystallization where the degree of solid solution is immensely greater, as in the case of the micas and the amphiboles. Owing to this complex isomorphism,
1 Cf. Allen & Clement, Amer. Journ. Scz., ser. IV, vol. xxvi, pp. 101-18, 1908.
472 Reviews—F. W. Harmer—COrag Mollusca.
this part of the theory is tentative and the details are liable to modification. When the theory is considered in relation to the actual intrusion or extrusion of the rocks, several difficulties arise. The first of these is concerned with the sequence of igneous intrusion. Bowen considers that the intrusion of basic into acid material is due to movements during cooling, and that the absence of granitic upper layers is sometimes due to denudation. In the ‘‘ Younger Igneous Rocks”? of the Scottish Highlands the sequence is from peridotite to granite, with the acid rocks always intrusive into the basic. As several of the former are found in contact with the schist roof, the acid layers cannot have been denuded away, and it is difficult to understand the mechanics of the differentiation and intrusion, particularly if the former be considered to have occurred in situ. A related point is concerned with the intrusion of batholiths, as the theory takes no account of the material into which the batholith is intruded. It also seems to the writer that some of the later igneous rocks must partly owe their composition to refusion, and possibly absorption, and that they are not all direct differentiates of a primary basaltic magma. Yet, on the whole, the theory may be regarded as the most satisfactory advanced so far, particularly with regard to those parts of it which do not depend on any great extrapolation from the synthetic work. AS:
Il.—Tue Puriocene Moxtusca or Grear BriraIn, BEING SUPPLE- MENTARY TO S. V. Woon’s MonocrapH oF THE Crac Mortusca.' By F. W. Harmer, F.G-S., F.R. Met.S., ete.
‘]\HE rich remains of Pliocene Mollusca which characterize ae Crag
deposits of East Anglia have long been familiar to the palzo- conchologist through Searles Wood’s classic memoir on that subject, which was issued in parts by the Paleontographical Society between the years 1848 and 1882. Few fossiliferous regions have been so popular with the collector and student as the counties of Norfolk, Suffolk, and Essex, which have yielded the Crag fauna, doubtless by reason of their easy accessibility from London and the numerous open crag-pits from which specimens could readily be obtained.
It ies been inevitable, therefore, since the completion of Wood’s work, now more than thirty years ago, that a large amount of further material has been acquired, the study of which has rendered necessary the recognition of many new forms and a revision of the older nomenclature. This is the special task which the author of the present memoir has set himself to accomplish, and for which, we think, he is particularly well qualified to undertake. It is interesting to note that Mr. Harmer was the great friend of Searles Wood, the younger, and a co-worker with him in unravelling the history of the Crag formations, he himself becoming the author in later years of many valuable contributions on the same subject, so that at the present day he may be regarded as one of our best authorities on the Pliocenes
1 Pt. i, pp. 1-200, pls. i-xxiv; pt. ti, pp. 201-302, pls. xxv—-xxxil. Published by the Paleontographical Society, 1914; 1915. (Pt. iii now in the press.)
Reviews—F. W. Harmer—Crag Mollusca. 473
of this country. He has, moreover, collected from the more important Continental deposits of Pliocene age, and has made himself familiar with the priceless collections of later Tertiary Mollusca preserved in the Museums of France and Italy.
The particular material on which this memoir is based was obtained from excavations carried out at Little Oakley, near Harwich, which has furnished a prolific molluscan fauna of Red Crag or ‘ Waltonian’ age containing littoral, southern, and some northern species.
The two parts, now issued, comprise together 302 pages of text and 32 plates. Brief notices of these have already been published (Guot. Mae., 1914, p. 227; 1915, p.565; and Ann. Mag. Nat. Hist., ser. Vill, vol. xiii, p. 604, 1914), but, on account of the great importance of the work both to the paleontologist and the collector, it is thought that a further record of so valuable a work may be acceptable. In the early pages of the memoir the author introduces us to the non-marine shells of the Crag period under the groups ‘‘ Terrestrial’? and ‘‘ Aquatic”, comprising nearly fifty species, of which about one-fourth are regarded as extinct, while all have been previously described elsewhere. The distribution of these forms is set ont ina tabulated scheme showing that they are best represented in the Norwich Crag, fewer species occurring in the Red Crag, while only three have been recognized in the Coralline Crag.
The author next proceeds to the consideration of the marine Gastropoda, of which over three hundred species and varieties are at present discussed, more than eighty being regarded as new. These species are treated under the following genera and subgenera: Zrivia, Voluta, Ancilla, Terebra, Columbella, Astyris, Cassidaria, Cassis, Semicassis, Rostellaria, Rimella, Nassa, Desmoulea, Buccinum, Liomesus, Purpura, Stenomphalus, Triton, Murex, Ocinebra, Urosalpinz, Trophon, Meyeria, Searlesia, nov., Parasipho, -Anomalosipho, Volutopsis, Beringius, Neptunea, Fusus, Sipho, Pleurotoma, Hemipleurotoma, _ Clavatula, Genotia, Pseudotoma, Borsonia, Oligotoma, Drillia, Spiro- tropis, Clathurella, Bellardiella, Mangilia, Hedropleura, Raphitoma, Bela, and Taranis.
_ Clear diagnostic characters ‘are furnished of each species or variety, followed by full information respecting geological and geographical distribution. It is noticeable that a few of the generic names have been attributed to pre-Linnzan authors, whereas, according to the laws of zoological nomenclature, the author should be quoted who first adopted such from the time of Linneus and upwards. Therefore, we think it preferable to write Zerebra (Adanson, 1757), Lamarck, 1799; Fusus (Klein, 1753), Lamarck, 1799; and so on. Again, some of the generic names appear to be preoccupied in other sections © of zoology, as, for instance: Zriton, of De Montfort, 1810, which had been previously used by Linneus for one of the Cirripedia, and hence we think Schumacher’s Zampusia should take its place; Meyerza, of Dunker & Metzger, 1878, was applied by McCoy to a Crustacean in 1849, and must, therefore, be replaced by Norman’s Jetzgeria of 1879; Klein’s Sipho, adopted by Morch in 1852, differs from that of Fabricius of 1828, and thus, according to the late G. F. Harris (Cat. Australasian Tert. Moll. Brit. Mus., 1897, p. 152), Beck’s Zritonofusus
474 Reviews—R. H. Rastall’s Agricultural Geology.
of 1847 should be accepted; lastly, Bolten’s Zwurrzs of 1798 has priority of Plewrotoma, of Lamarck, of 1799. Few systematic works on paleontology are entirely free from blemishes connected with nomenclature, and it is only by persistently calling attention to them that we may hope to guard against similar errors in the future. This criticism, therefore, is offered in no captious spirit, being considered ~ to detract in no way from the great excellence of the work which, when completed, will rank as a valuable guide and reference book to the history of the later Tertiary Mollusca of this country. Special mention should be made of the beautiful photographic figures prepared by Mr. J. Green, which form the plates that adorn the monograph. Not only are the British Crag shells figured in this way, but illustra- tions are frequently given side by side of recent and foreign specimens for purposes of comparison. Thus, the author attains an accuraey in his determinations which will be of inestimable importance, not only to the paleontologist but also to the collector, who will almost be able to name his shells without reference to the text.
The work appears to be a long way from completion, but we earnestly trust that, when the last part is in preparation, the author will provide us with an ample index so that every specific and generic name used, whether in synonymy or elsewhere, shall be brought out alphabetically. With such an adjunct the utility of this valuable memoir will be very greatly enhanced.
ITI.—Acricutrurat Grotocy. By R. H. Rasrarz, M.A. 8yo; pp. x + 332. Cambridge University Press, 1916.
[]\HE place occupied by geology in an agricultural curriculum varies
so much in different universities and other institutions that the task of writing a suitable textbook is a peculiarly difficult matter, and we welcome this conspicuously successful attempt by so competent a geologist as Mr. Rastall to fill a gap that has long existed. About half the text is taken up by chapters on Minerals and Rocks, Weathering, Transport and Corrasion, Sediments, Superficial Deposits, and Soils, including most of those matters that are of primary importance from an agricultural point of view. These are models of their kind, as might be expected from one of our leading petrologists. The literature on soils is so scattered, and so little has . been attempted in this country by way of soil surveys, that all those concerned with scientific agriculture are indebted to the author for his able correlation of the chief available facts. He regrets in his preface that considerations of space have prevented the inclusion of full details on the subject of mechanical soil analysis, but we hope these will find a place in the next edition, though of course aware that they have been ably treated by Mr. A. D. Hallin his well-known works. The essential facts of water supply and drainage are clearly set forth in chapter vii, the page on ‘‘dew ponds’? being of particular interest. Then follows a chapter on geological maps and sections, which would be much improved by a few cuts to illustrate the chief kinds of map in common use. The rest of the book is mostly occupied by well-balanced chapters on stratigraphy, the one
Reviews—C. Reid & J. Groves—Purbeck Charas. 475
thing lacking here being illustrations of a few leading fossils, just sufficient to help the student to recognize the chief fossiliferous strata as met with in the field. The last chapter, contributed by Dr. F. H. A. Marshall, embodies a most interesting and valuable summary of our knowledge of the geological history of the Domestic Animals. We only wish this chapter could have been more fully expanded. In conclusion, we congratulate Mr. Rastall on his admirable and luminous textbook, which should be in the possession of every teacher and serious student of agriculture.
J. R. A.-D.
TV.—Tue Purpeck Cuaras.
T last. we are promised some definite information about the interesting series of Chara, so common in the Purbeck cherts. Hitherto the nature of the matrix has only permitted a study of sections of these plants allowing of imperfect examination. But the labours of Messrs. Clement Reid & James Groves resulted in the finding of Chara remains in a close-grained limestone, which permitted a fresh method of treatment. On treating pieces of limestone with a steady drip of slightly acidulated water the results were surprising even to the experimenters. The irregular mineralization of the limestone allowed the dripping water to rapidly attack the pure calcite and to leave the silicified matter standing in relief. As the Characee proved to be not pure calcite they were among the standing forms after treatment. And the authors have not only been able to obtain reliefs of fruits and stems, but even, in many cases, completely to remove fruits and stems from the matrix. The amount of new material is so great that there may be seven or even eight species of four genera. But they are so broken up and entangled that it will take much research to work them out properly. The most abundant form, however, is fairly well known, and ‘Messrs. Reid & Groves have described it as Clavator, n.g., in Proc. Roy. Soc., B., vol. lxxxix, pp. 252-6, pl. viii, 1916; no trivial name is given, nor Is any type quoted, unless Messrs. Reid & Groves wish it to be understood that Saporta’s species (the only one mentioned) is to be so regarded. The editor is at fault in passing this omission. The paper is of remarkable interest and importance.
V.—Tue Corretation or tHE Pre-Camprran Rocks or THE Recion oF THE Great Lakes. By A. C. Lawson. Bull. Dep. Geol. Univ. California, vol. x, No. 1, pp. 1-19.
N this paper the author endeavours to draw up a correlation table for the pre-Cambrian rocks of Canada, based on the hypothesis that there have been in the region named two and only two great periods of granitic intrusion, each followed by its concomitant uplift and denudation, this constituting a major unconformity. The classification on this basis when reduced to its simplest terms is as follows:
(1) Ontarian system, including the Coutchiching, Keewatin, and
Grenville series. (2) Laurentian revolution, that is, the intrusion
of the granite batholiths. (3) Epilaurentian interval, when the
476 Correspondence—Leonard H. avwkes.
foregoing underwent extensive denudation. (4) Huronian system, including the Bruce and Temiskamian series. (5) Algoman revolution: the intrusion of the Algoman granites. (6) The Eparchzan interval of denudation. (7) This was followed by the deposition of. the Animikian and Keweenawan series, forming the Algonkian system, which the author prefers to regard as being the base of the Paleozoic. This concise statement will do much to simplify and render clear a subject in which much confusion has hitherto prevailed, largely owing to an unnecessarily cumbrous nomenclature, but partly also due to uncertainty in the correlations.
VI.—Mouscuerratk IcurHyosaurs.—Von Huene’s manuscript. on the Muschelkalk Ichthyosaurs, dated autumn, 1913, has just appeared in Pale@ontographica, vol. lxxii, pt. i, June, 1916. The work consists. of 68 pages, 7 plates, and 96 text-figures, and is of the greatest use for comparison and study. Von Huene describes the genera Mixosaurus, Cymbospondylus, Shastasaurus, Pessosaurus, and a new genus Pachygonosaurus, founded on a few vertebre in the Berlin Museum, indicative of two species to which no trivial names are assigned. ‘he illustrations are abundant and good.
CORREBSPON DEHN CEH.
. ROPY SURFACES OF LAVA IN ICELAND.
Srr,—In last month’s Grotocican Macazine, writing of the ropy lava surfaces so characteristic of large areas of the Icelandic deserts, I remarked on never having seen similar surfaces in the Tertiary series of Iceland, and added that they do not seem to have been noted in the British Isles.
I find, however, that basalts with ropy surfaces were observed in the Ferde Islands by Sir George Mackenzie and described by him to the Edinburgh Royal Society in1812. Mackenzie’s paper (‘l'rans. Roy. Soc. Edin., vol. vii, p. 218, 1814) contains a natural size illustration of ropy basalt. He writes: ‘‘The surfaces of many lavas which I passed over in Iceland were not unlike coils of rope or crumpled cloth, an appearance which we should expect to be assumed by any viscid matter in motion., On our first visit to the island of Naalsde we observed the surface of a bed of amygdaloid, which had been exposed to a considerable extent by the removal of the bed above, exhibiting an exact picture of the lavas I had seen in Iceland” (p. 221). Mackenzie states that whatever doubt may have previously existed in his mind as to the igneous origin of the ‘trap’ was dissipated by the discovery of these ropy surfaces.!
Leonard HawkEs. GLASGOW.
‘ In reference to the footnote to my paper, GEOL. MAG., Sept. No., p. 390, I find that Dr. Pjetursson now regards his ‘‘ Graa Etage’’ of Middle Northern Iceland as of Post-Tertiary age. This view presents difficulties, and I prefer to hold to his former idea as there indicated. ‘The doubt I expressed relates, not to the Tertiary age of the ‘‘Graa Htage’’, but to the adequacy of the evidences therein of a general ‘‘ glacial period’’.
Correspondence—Marion I. Newbigen. ATT
THE LATE PROFESSOR JAMES GEIKIE.!
Sir,—A biography of the late Professor James Geikie is now in course of preparation, and the work would be greatly facilitated if those who have letters or communications of general interest from him would kindly forward these to me at the Royal Scottish Geographical Society’s Rooms, Synod Hall, Castle Terrace, Edinburgh. They will be carefully preserved and returned after being copied.
EDINBURGH, ~ Marton i NEWBIGEN.
September 4, 1916.
QS Eni ALE ya
JAMES DALLAS, F.S.A.Scor. Born 1853. DIED SEPTEMBER 12, 1916. Wr regret to record the death, in his 63rd year, of Mr. James Dallas (formerly curator of the Albert Museum, Exeter), which occurred on September 12, at Bampton, Oxon. James Dallas, F.S.A.Scot., was the son of the late W. 8. Dallas, F.L.S., for so many years Assistant Secretary to the Geological Society of London.
CHARLES DAWSON, F.S.A., F.G.S.
BORN JULY 11, 1864. DIED AUGUST 10, 1916. GroLocists and archeologists alike mourn the early death of Mr. Charles Dawson, of the Castle Lodge, Lewes. For thirty years he had been one of the most active students of the geology and antiquities of Sussex. To a capacity for taking pains, with endless patience, he added a sharpness of sight that never overlooked any- ‘thing of importance; and he was not only in close touch with all workmen in his district who might make accidental discoveries, but was also in constant friendly communication with a wide circle of ‘professional scientific men who helped him to make the best use of his material.
Charles Dawson was born at Fulkeith Hall, Lancashire, fifty-two years ago, the son of Mr. Hugh Dawson, barrister-at-law. Most of his early life was spent at St. Leonards-on-Sea, and he was educated at the Royal Academy, Gosport. He began to study law in 1880, and from 1890 until the time of his death he practised as a solicitor at Uckfield. There he held several public appointments, and won the highest esteem of all who were associated with him. His duties were many and arduous, and science was the recreation of his leisure hours.
From early boyhood Mr. Dawson had been interested in natural history and antiquities, and he began to collect Wealden fossils from the quarries and cliffs round Hastings. He soon attracted the notice of Mr. S. H. Beckles, F.R.S., who was then spending his last years at St. Leonards. He was thus helped and encouraged to collect Dinosaurian remains in a systematic manner; and he met with so much success that by 1884 he had made a valuable collection which
1 For a brief account of Professor James Geikie and his works, see ‘‘ Hminent Living Geologists’’ (GEOL. MaG., N.S., Dec. V, Vol. X, No. VI, June, 1913, pp. 241-8, with a portrait, Pl. IX); for obituary see op. cit., April, 1915, p. 192.
478 Obituary—Oharles Dawson.
was gladly accepted by the British Museum. From that time until nearly the end of his life he made continual additions to the Dawson Collection, as it was named by the Museum, where it now occupies a conspicuous position. The last noteworthy accession to it was the finest known specimen of the Wealden ganoid fish, Lepidotus mantelli. On the death of Mr. Beckles in 1890, Mr. Dawson also gave much help to the British Museum in labelling the collection of Wealden fossils which was acquired from that gentleman’s executors.
Among the Wealden Dinosaurian remains discovered by Mr. Dawson, Mr. Lydekker recognized three new species of Jyuanodon, of which one was named J, dawsont. Among his later discoveries was the first tooth of a Wealden mammal, Plagiaulax dawson. He obtained this specimen from one of the fine pebbly bone-beds which occur in different horizons of the Wealden series. He subsequently encouraged two French students at the Hastings Jesuit College, Fathers Teilhard de Chardin and Pelletier, to examine these bone-beds more thoroughly, and they succeeded in finding a second form of mammalian tooth, Dipriodon valdensis, besides numerous rare teeth of reptiles and fishes. Mr. Dawson was also the stimulating friend of Mr. Philip Rufford, who made the great collection of Wealden plants now in the British Museum.
While interested chiefly in the fossils of the Wealden formation, Mr. Dawson also paid much attention to its more purely geological features, and he made one important investigation of the natural gas at Heathfield, which he described to the Geological Society in 1898. He also exhibited zincblende from the Wealden and Purbeck beds to the same Society in 1913.
Mr. Dawson’s most important archeological work culminated in his publication of the two handsome volumes on the History of Hastings Castlein 1909. His interest in geology, however, gradually led him to turn to prehistoric archeology, and during his later years he searched most persistently the superficial deposits of Southern Sussex. His ultimate success was his recognition of the great antiquity of the Piltdown gravel, and his discovery in this deposit of the skull and mandible of the oldest known type of man, Hoanthropus dawsont, which was described to the largest meeting of the Geological Society ever assembled in December, 1912. The story of this discovery, which was not altogether accidental but the outcome of logical reasoning, is now so well known and has been so often repeated that it need not be further detailed here.
Mr. Dawson made few contributions to geological literature—he preferred to hand over his specimens to experts who had made a special study of the groups to which they belonged. He published only one paper in the Grotoeican Maceazine, on ‘‘ Dene Holes, Ancient and Modern’’ (1898, p. 293), concluding that they were all mines. His only contributions to the Geological Society’s Quarterly Journal were those on Natural Gas and the Piltdown Man already mentioned. His last paper, read to the Anthropological Institute in 1915, was an ingenious comparison between the shapes of the so-called ‘ Koliths’ of tabular flint and the shapes of diminutive splinters obtained from the hexagonal columns of starch. He maintained that tabular flint
Obitwary—Robert John Lechmere Guppy. 479
had an imperfect hexagonal structure, and that accidental fractures must produce the shapes found in ‘ Koliths’.
Mr. Dawson was a most versatile student, and during the beginning of his last illness was investigating a case of the development of incipient horns in a cart-horse. He had a restless mind, ever alert to note anything unusual; and he was never satisfied until he had exhausted all means to solve and understand any problem which presented itself. He was a delightful colleague in scientific research, always cheerful, hopeful, and overflowing with enthusiasm. The premature loss of his inspiring and genial presence: is indeed a great sorrow to his large circle of devoted friends. Aa S aa
"ROBERT JOIN EECHMEREYGUPRY, Corresponding Member of the Zoological Society of London and of the New York and Philadelphia Academies of Science.
Born Auaust 15, 1836. Diep AuGusrT 5, 1916.
We deeply regret to announce the death of Robert John Lechmere Guppy, 1n the Island of Trinidad, on August 5, 1916, who was within a few days of completing the 80th year of his age. The deceased was born in London in 1836, his father being the Hon. R. Guppy, M.A., Barrister-at-law, and for many years the Mayor of San Fernando, Trinidad. He qualified for a Civil Engineer, and after- wards travelled through Australia, Tasmania, and New Zealand. On returning he joined his family at Trinidad and became engaged in the construction of the Cipero Railway, subsequently entering the Colonial Secretary’s office, and in 1868 was appointed to the important. position of Chief Inspector of Schools, which he held until retirement in 1891. He was an ardent student of natural history and foremost in supporting the scientific societies of his island home, having been president of the Scientific Association of Trinidad and the first elected ‘presiding officer of the Royal Victoria Institute Board. He was particularly interested in the Marine Mollusca, and was instrumental in obtaining for the British Museum the second largest example of a living species of Plewrotomaria known to conchologists, having a height of 150 millimetres. The shell was obtained from off the Island of Tobago, and was described by Guppy in a locally published journal. : ;
Mr. Guppy’s scientific labours will always be associated with his investigations on the geology and paleontology of Trinidad and other regions of the West Indies. Until his researches began the only information on the geology of Trinidad was obtainable from Wall and Sawkins’ ‘‘ Report ”’ of 1860, published by the Geological Survey of England, the paleontological portion of which was furnished by the late R. Etheridge, F.R.S., who regarded the Tertiary fossils as belonging probably to the Miocene period. Guppy’s first papers referred to the Foraminiferal beds of San Fernando, containing numerous Orbitoides and other forms, as well as Brachiopods, Kchinoids, and Crustacea, which were described and figured and assigned to the older Miocene. It was found that these fossils bore resemblances to those from the Farallon rock which enabled both sets
430 Obituary—Robert John Lechmere Guppy.
of beds to be regarded as of contemporaneous origin and belonging to the older Miocene. At a later date, however, a similar fauna was reported from beds in the Island of St. Bartholomew, associated with corals of a pre-Miocene facies, described by Duncan, which resulted in the Farallon Rock, the San Fernando, and St. Bartholomew Beds being correlated together and recognized as of Kocene age or Lower Oligocene of later authors. So far as is known at present, the oldest | Tertiary beds at Trinidad occur in the Soldado Islet, where the lowest fossiliferous deposits have yielded, according to Miss C. J. Maury’s monograph on the Paleontology of Trinidad (Journ. Acad. Nat. Sei. Philadelphia, ser. 11, vol. xv, 1912), Venertcardia planicosta, a well- known Kocene Pelecypod of Alabama and Europe.
It is possible, therefore, that the Tertiary fossils from other districts of Trinidad, many of which have been described and figured by Guppy, are younger than those found in the Soldado, Farallon, or San Fernando deposits, although their horizons as given by Guppy are not always in agreement with the views of Miss Maury, an ~ instance of which may be quoted in respect of the Manzanilla Beds, which the latter regards as Lower Oligocene, whereas Guppy and Dall schedule them as Eocene. Further studies are required in this direction before a more accurate correlation of these rocks can be attained. Guppy wrote several memoirs on the geology of other West Indian islands and Venezuela, and studied other Tertiary material, especially from Jamaica, San Domingo (Hayti), Antigua, Tobago, etc., some of his type "Mollusca from Jamaica and San Domingo being preserved in the Geological Department of the British Museum. He was of opinion that ‘the Caribbean Miocene fauna resembled that of Bordeaux, Dax, etc. (these French beds now being regarded as Oligocene or uppermost Kocene), rather than the American Miocene (Quart. Journ. Geol. Soc., vol. xxi, p. 285, 1866). Mr. Guppy was a prolific writer on his subject, some of his best memoirs having been published by the Geological Society of London, to which he was elected a Fellow in 1866, but he resigned in 1882. Although his views on ‘‘ the existence of an Atlantis in the early Tertiary period ” have not been generally accepted by geologists, such a fact should in no way minimize the great importance and value of his paleontological researches on the West Indies, which will always form the basis of similar work that may be undertaken by any future investigators. Mr. Guppy has contributed no fewer than fifty-one papers to various scientific journals, and with one exception (a paper on Australian geology) the whole series deals exclusively with the geology and paleontology of the West Indies. From 1864 to 1900 he contributed fifteen papers to the GroLoeIcaL Magazine. Having known Mr. Guppy personally for many years we would wish to offer our sympathy to the widow and family in their bereavement. Rabe,
Erratum.—Dr. C. A. Cotton desires to correct an error in his paper, ‘‘On the Geological Structure of New Zealand”’ (see Gron. Mae., June, 1916). On p. 247, line 36, for ‘left’ read ‘continuously’ above water.—Ep. Grou. Mae.
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THE
GEOLOGICAL MAGAZINE
NEVES RIES DEG ADE VOLT obi: No. XI.—NOVEMBER, 1916.
ORIGINAL ARTICLHS.-
J.—Eocenr \Corats From THE Fry River, Centran New Guinea. By J. W. GREGORY and JEAN B. TRENCH, University of Glasgow. (PLATES XIX-XXIL)?!
We are indebted to the Trustees of the Carnegie Trust for the Universities of Scotland for a grant to cover the cost of the plates in illustration of this paper. We are also grateful to Mr. 8. Fingland for the care taken in preparation of the photographs.
URING the expedition in 1889 and 1890 by the Right Hon. Sir William Macgregor, G.C.M.G., etc., up the Fly River, the largest river in New Guinea, he madea collection of fossil corals and limestones which he has entrusted to us for description. The specimens are rolled pebbles collected from the bed of the river, which flows between alluvial banks through low forest-clad country. Rocks were only exposed in occasional “bars across the river, and there is no evidence as to their succession or dip.
The narrative of the expedition by Sir William Macgregor (1890,
p. 56)” records the occurrence of pebbles of petrified coral, flint, and Beechous, at a little south of Macrossan Island, at the latitude of about 6° ‘5! 8S. He records limestone also at 5° "40'S. at the con- fluence of the Black River with the Palmer, which is the chief upper tributary of the Fly River. Sir William Macgregor considered it possible that the pebbles might have been washed down from the lofty riountain chain which he discovered at the head of the Palmer River, and which includes Mt. Bliicher in German New Guinea and Mt. Donaldson within British territory. The pebbles do not, however, appear to have travelled far down-stream, and the record in Sir William Macgregor’s journal of the association of flint, limestone, and petrified coral below Macrossan Island suggests that the collection was made there. It consists of specimens of compact coral limestone, in which the coral material is brown, while the matrix is cream- coloured. One specimen (No. 20) consists of white limestone, and in it many of the loculi of the coral are empty ; it may be younger in age than the rest of the collection. There are some fragments of white compact chert, in which the sections cut show no definite organisms; also a silicified coral, and a series of foraminiferal lime- stones, which are being investigated by Mr. R. B. Newton.
1 Plates XIX and XX accompany Part I, and Plates XXI and XXII will appear with Part II of this paper in the December Number. 2 A full summary of the narrative is given in Dr. Thomson’s useful work, British New Guinea, 1892, pp. 117-54.
DECADE VI.—VOL. III.—NO. XI. 31
482 J. W. Gregory & Jean B. Trench—
The bulk of the corals and the foraminiferal rocks appear to have come from the same limestone, which is of Eocene and probably of Middle Eocene age. The cherts are probably Upper Cretaceous. The map in Mr. Gibb Maitland’s valuable but often overlooked memoir (1893, Map No. 3) colours the whole of the country along the Fly River, even to the north of 6°, as ‘‘ recent superficial deposits’’, for the rock exposures on the river bed would be too small to be shown on that map.
Coral limestones have been repeatedly recorded from the interior of British New Guinea, but the references to them in the literature convey the impression that they have been regarded as young raised reefs, and therefore evidence of a great uplift in recent times. Mr. Gibb Maitland records the coral limestones on the Aird River in latitude ° 7° 10’ S. as ‘‘raised coral reefs’’; and the same view has been adopted (e.g. Gibb Maitland, 1898, p. 63) for limestones as much as 2,000 feet above sea-level. The Eocene age of Sir William Macgregor’s corals suggests that the higher coral limestones may be
.older than has been supposed. Dr. Logan Jack (1894, pp. 93, 94) has identified a fossil collected by Sir William Macgregor from the Purari River as a Cretaceous Belemnite. ‘The genus Actenacis, which is represented in the collection by two species, is more frequent in the Cretaceous than the Eocene; the specimens of A. maitlandi are identical in lithological character with the brown Kocene corals and are doubtless Hocene. The other Actinacis we identify as A. swma- traensis (Tornq.); it is in a white chert and is probably Cretaceous.
The list of species is as follows :—
Feddema sp. Kobya hemicribriformis, n.sp. Circophyllia sp. Actinacis maitlandi, n.sp. Stylina macgregori, n.sp. A. sumatraensis (Tornq.). Stylophora papuensis, n.sp. Porites deshayesana, Mich., var. Leptoria carnei, n.sp. mequisepta, n.var. Plesiastrea horizontalis, n.sp. Porites sp.
Dachiardia macgregori, u.sp. Montipora antiqua, n.sp.
Systematic Dxrscriprion.
The collection includes three simple corals which are shown by the abundant dissepiments to be Astreans; but as only transverse sections are available the material is inadequate for specific description.
Frppenia, Duncan, 1880.
Two specimens (Nos. 17 and 21) have flattened sides, paliform lobes to the two first orders of septa, and have no columella; they agree with Feddenia from the Ranikot group, Lower Eocene, Sind. The diameter of the corallitesis 10 X 15mm. In No. 17 the number of septa is forty. Both specimens occur in a yellow foraminiferal limestone.
Circopuyitiia, Ed. & H., 1848.
This coral (No. 25) has an elongated cross section with parallel sidesand rounded corners. The wallsarethin. The columellais large and trabecular. There are no pali. The coral is therefore clearly a Circophyllia, which is atypically Eocene genus. A smallincomplete
Eocene Oorals, Central New Guinea. 483
section on the same specimen shows a strong resemblance to the figure by Reis (1890, p. 108, pl. iv, fig. 17) of his Desmopsammia perlonga, for it has broken thin irregular septa, on which occur triangular paliform expansions. The section is, however, probably across a young Circophyllia in which the septa are thin and incomplete, and the columella is represented only by isolated trabecule from the septa.
\
SrytopHora, Schweigger, 1819. Stylophora papuensis, n.sp. (Pl. XX, Fig. 3.)
Diagnosis.—Corallum compact and formed of tufts of crowded branches which are circular in transverse section except near their bifurcations, where they give rise to elongated or dumb-bell sections. The branches are usually hollow. Surface granular and punctate. Corallites small and rounded. Calices arranged irregularly and sparsely, their distance apart being generally greater than the diameter of the corallites. They are shallow and their margins are flush with the surface of the corallum and show no sign of a raised rim. Septa six in number and regular in arrangement; they are thick and joined to the columella. No secondary septa. Columella prominent.
Dimensions.—Corallum, 45 long, 60 broad, 30mm. thick; diameter of branches, 3-4mm.; diameter of corallites, -6mm.; distance of calicinali centres, 1-2 mm.
Figures.—P1. XX, Fig. 3, part of surface of corallum, x13 diam.
A finities.—S. papuensis show a close resemblance to the Eocene ‘species S. rugosa (d’Arch.),! agreeing with the latter in the size and irregular arrangement of the calices, in the prominent columella, and the granular surface. It differs, however, by having neither secondary septa nor rim around the calices.
Stylophora has a wide range through the Kainozoic limestones of Sind. Duncan has thence described four species. Of these S. contorta, Leym., from the Khirthar Series (Duncan, 1880, p. 61, pl. xviil, figs. 21, 22) is widely distributed through the Eocene; it is dis- tinguished from S. papuensis by having more crowded and larger calices and conspicuous secondary septa. ‘lhe nearest Indian species is the S. pulcherrima, Ach., which has been described from Sind by Duncan (1880, p. 73, pl. xv, figs. 12, 13) in the Nari Series, which he correlated with the Oligocene or Upper Eocene. The Sind representa- tive of the species agrees with S. papuensis by having a granular surface and only six septa; but in S. pulcherrima the corallum is flat and massive instead of being dendroid. Of the two Miocene species from Sind, S. mznuta, Duncan (1880, p. 83, pl. xxii, fig. 6, originally described by Duncan from the West Indies) has a smooth surface and more distant calices, each of which is surrounded by a thick circular rim; while S. confusa, Duncan (1880, p. 83, pl. xxiii, fig. 7) has crowded calices, a nodular corallum, and the inter- calicinal distance is only about 1 mm.
1 D’Archiac, 1847, p. 1010; 1850, p. 403, pl. viii, fig. 7.
484 J. W. Gregory & Jean B. Trench—
Sryrina, Lamarck, 1816. | Stylina macgregort, n.sp. (Pl. XIX, Figs. 1a, 0.)
Diagnosis.—Corallum massive, with a subplane upper surface. Calices irregularly distributed and irregular in shape. They are shallow and sunk between broad ribbon-like and apparently solid walls, over which the costz were no doubt continued as prominent lines. Septa three cycles. The primary septa are much thicker than the others and very conspicuous. The hexameral symmetry of the septa is usually complete. Both secondary and primary septa join the columella; but the secondary septa are much thinner than the primary. :
Dimensions.—Fragment of corallum, length, 60 mm.; width, 30 mm. ; corallites, diameter, 4-5 mm. ; calicinal centres, average distance, 8mm.
Figures.—Pl. XIX, Fig. la, part of the upper surface of the corallum (No. 27), magnified 3 diameters; Fig. 1b, part of a polished surface of the same specimen, magnified 3 diameters.
Affintties.—This species, owing to its septal plan, belongs to the same group as the type of the genus, S. echinulata, Lam., from the Middle Oolite, but its calices are much larger. The most conspicuous feature in the species is the prominence of the primary septa, whereby it has a striking external resemblance to a Miocene coral from Egypt—Stylophora asymmetrica (Gregory, 1898, pl. viii, fig. 4); but the transverse section, Pl. XIX, Fig. 1, shows, however, that there is no true coenenchyma, and that the coral is one of the Stylinide. The species, owing to the conspicuousness and irregularity of the primary septa, the continuation of the coste over the thick wall, and the thickness of the columella, also remarkably resembles a coral from the Pliocene of Java described by Felix (19138, p. 336) as Srderastrea micrommata. ‘The transverse section of the coral shown by Felix (ibid., fig. 3) seems to us to prove that it is not a Srderastrea, the intimate structure of which has been well represented in sections by Dr. Ogilvie (1895, p. 181). Felix’s S. mecrommata appears to have the character- istics of a true Stylina. It differs, however, from the species collected by Sir William Macgregor, since the corallites are more crowded and are only from 13 to 2 mm. in diameter. The nearest ally of S. macgregort is Stylina tertiaria, Duncan (1880, p. 61, pl. vi, figs. 1, 2), from the Khirthar Series of Sind. ‘The two species agree by the great length of the coste and the spacing of the corallites. But they differ in that S. tertiaria has only two complete cycles of septa and as its primary septa lack the unusual thickness of its New Guinea ally.
It is advisable also to compare the coral with S. reuss?, Duncan, from the Lower Eocene or Ranikot Series of Sind (Duncan, 1880, p. 80, pl. x, fig. 11). But in that species the corallites are smaller, being only 2 mm. in diameter ; they are very irregularly spaced and have less conspicuous primary septa. S. macgregori of Sind therefore agrees better with the Upper Eocene than with the Lower Eocene species from Sind. The matrix of this specimen differs from that of other corals as it is white and contains open spaces; it may therefore come from a different horizon.
Eocene Corals, Central New Guinea. A485
Leprorra, Ed. & H., 1848.
Leptoria carnei,! n.sp. (Pl. XIX, Figs. 2 and 3.)
Diagnosis.—Corallum, external form unknown. Calicinal valleys long, and branching rather angular; they are irregularly arranged. Corallites, walls vary in thickness from a mere line which is no thicker than a dissepiment to that of the thickest part of the septa. Dissepiments most abundant nearest the walls. Septa, serration very slight ; all the septa in a considerable series are often equal in thickness. Septa become thicker distally and end in a cross-shaped T-piece, the length of which is from two to five times the thickness of the adjacent part of the septum. Columella irregular in thickness ; in places only as thick as the thinnest part of the septa; it may then be discontinuous, but it is usually a continuous lamina, and its thickness may be equal to the thickest part of the septa.
Dimensions.—Length of calicinal valleys, 16-35 mm. ; breadth of calicinal valleys, 8-15 mm. ; septa, about 10 in 10 mm. 5
Figures.—P\. XIX, Fig. 2, part of a polished surface (No. 6 type-specimen) showing the well-defined narrow wall with abundant adjacent dissepiments, and, opposite the arrow, the T-shaped ending of the septa and the thin, irregular columella; x 3 diam. Fig. 3, part of another specimen (No. 7 co-type) showing (beside the two dots) the conspicuous wall; in the centre of the figure the expanded ends of the septa are cut through obliquely, and the columella is thin and discontinuous; the dissepiments are especially numerous; xX 3 diam.
Affinities. —The equality of the septa at first suggests comparison of this species with the Mfeandrina equisepta, Gregory (1900, p. 212, pl. xix, fig. 2), from the Miocene of Christmas Island, but that coral has the columella of a true Meandrina (using the name Meandrina in the sense of Edwards & Haime, and not of its original founder, Lamarck).
An Indian coral which was described by Duncan (1880, p. 39,
_pl. vi, figs. 11, 12) as Diploria flecuosissima, D’Arch., is suspiciously
like the species in its septal characteristics, but the Sind coral has the separated walis of Diploria. Duncan’s Meandrina medilicott: (1880, p. 77, pl. x, figs. 15, 16), from the Nari Series (Oligocene), is, however, not a Meandrina, but a Leptoria, as it has a very thin laminar columella; it differs from Z. carnei, which is its nearest ally, by its calicinal valleys being far more sinuous, its wall thicker, and the adjacent septa, though sometimes equal, usually being alternately large- and small; it has, moreover, about forty septa to the inch. L. concentrica, Duncan (1880, p. 87, pl. xxiii, figs. 1, 2), which ranges from the Khirthar or Nari Series to the Gaj, differs by having the septa alternately large and small, while the inner ends of the larger septa are club-shaped rather than T-shaped. J. radiata, Michelin (1847, p. 294, pl. Ixviii, fig. 3), from the Craie tuffeau (Turonian, Baines de Rennes), has long, straight calicinal valleys, which give the corallum its radiate aspect, and its septa are four to 1mm.
* Named after Mr. J. E. Carne, of Sydney, in recognition of his valuable
additions to the geology of New Guinea, as well as of his many important con- tributions to that of Australia.
486 J. W. Gregory & Jean B. Trench—
Dacurarpia, Duncan, 1880.
Dachiardia macgregori, u.sp. (Pl. XX, Figs. 2a, 6.)
Diagnosis.—Corallum nodular; growth irregular; in places the surface is subplane and granular. The calices are widely isolated by compact exothecal tissue. Elsewhere the corallites project above the surface and are therefore free laterally ; and the formation of younger similar surfaces has left spaces filled with matrix in which the corallites are laterally free. Corallites circular, subcircular, and sub-hexagonal; often long and straight; fission exceptional. Septa two complete cycles which are long and join the columella, and occasional representatives of a third cycle. Endotheca scanty. Columella small but distinct. In some sections it appears even styliform. Pali indistinct, occurring as paliform lobes.
Dimensions.—Diameter of corallum, about 50mm. ; diameter of corallites, 2-4mm.; distance of calicinal centres, 5-7 mm.
Figures.—Pl. XX, Fig. 2a, part of upper surface of corallum showing corallites and granular surface; x 3diam. Fig. 26, part of same specimen, showing transverse section of a corallite; x 2 diam.
A finitves.—This interesting coral raises the question of the affinities of the genus Dachiardia which, when founded by Duncan in 1880, was placed next to Plesvastrea; he, however, remarked at the end of the diagnosis (p. 92), ‘‘Fissiparity occurs, but israre.” Subsequently in his Revision (1884, p. 101) he placed the genus amongst the fissiparent Astreans, in the alliance Luvordea. His figures of D. densa, the first of the two species which he included in the genus, show no clear evidence of growth by fission. The figure of his second species, D. lobata, gives clearer evidence of that mode of growth, and is therefore the most convenient type.of the genus; we select it since none has been previously nominated.
D. lobata differs from D. macgregort by having twenty-four septa which are alternately large and small, so that the cycles do not retain — their hexameral symmetry. The calices in D. lobata are from 2 to 21mm. in diameter, and are therefore only half the size of those in D. macgregort. D. densa differs by having smaller corallites and three cycles of septa, which, being relatively longer, appear far more crowded than in D. macgregort. D..densa also has more definite pali.
Prestastrma, Ed. & H., 1848. Plesiastrea horizontalis, n.sp. (Pl. XX, Figs. 1a, b.)
Diagnosis.—Corallum compact, nodular. Outer surface unknown. Corallites circular to subcircular; long, straight, and parallel. They are united by horizontal dissepimental exotheca which gives a tabulate aspect to vertical sections, but may not be visible in cross- section. Septa three complete cycles, all short; in those of the third cycle the cost are sometimes twice as long as the corresponding septa. Pali two crowns forming a regular well-defined circle around the small fascicular columella. The secondary pali are no larger than the primary. Endotheca scanty.
Dimensions. —Diameter of corallites, 3mm.; distance of calicinal centres,
5mm.; diameter of circle of pali, 1-5mm.; average vertical distance between horizontal exothecal dissepiments, 5 mm.
Eocene Corals, Central New Guinea. 487
Figures.—Pl. XX, Fig. 16, part of a transverse section of specimen No. 18; x 3diam. Fig. la, part of a vertical section of the same specimen, showing the horizontal exothecal dissepiments ; x 3 diam.
Affinities. —This species is represented in the collection by four specimens (Nos. 9, 10, 18, 19), in some of which, however, the septal structure has been destroyed. Duncan has described a species, P. eocenica (1880, p. 66, pl. xix, figs. 8-10), from the Upper Khirthar or base of the Nari Series in Sind; it has more numerous septa, though the fourth cycle is not complete ; the septa of the third cycle are much longer and the corallites larger than in P. macgregort.
The well-known European Miocene species P. desmoulinsi, Ed. & H., 1851, has several resemblances to P. macgregori ; but it has a more compact exotheca and its primary pali are smaller than the secondary pali.
The specific name in Heliastrea tabulata, Martin (1880, p. 140, pl. xxiv, fig. 21, and pl. xxvi, fig. 4), from Java, suggests comparison with this species; but Martin’s illustrations show that his species is not a Plesiastrea.
Kosya, Gregory, 1900. Kobya hemicribriformis, n.sp.. (Pl. XXI, Fig. 4.)
Diagnosis. —Corallum massive ; external shape unknown. Corallites very large, closely crowded. Septa in four cycles which are generally complete. The primary septa are large and thickened with a paliform expansion at the inner end. Similar expansion and thickening also occur in some of the secondary septa, which are as long as the primary. The columella is large and it occupies a sixth of the diameter of the corallite. The alternate septa are usually eribriform and appear in sections as rows of isolated trabecule ; but in some of the younger corallites, owing apparently to a secondary thickening, all the septa may appear solid.
Dimensions.—Fragment of the corallum, No. 35, length, 70mm.; width, 5-5 mm. ; thickness, 40mm.; diameter of corallites, 12-14mm.; distance of calicinal centres, 12-22 mm. (average 15 mm.).
Figure.—Pl. XXI, Fig. 4, part of polished surface ; nat. size.
A finities.—This interesting coral is represented in the collection by six specimens (Nos. 30-5). They all appear to have come from the same bed, as they are in a light yellow limestone in which the matrix is paler in colour than the coral. The generic position of this coral is not free from doubt owing to uncertainty in definition of two genera. Dr. Andrews collected in the Miocene rocks of Christmas Island a small fragment of a coral which was included in Coscinareéa, as among the genera then established it was nearest to it, and the material was inadequate for the establishment of a new genus. The coral from New Guinea probably belongs to the same genus. Though the synapticule are scarce, they are quite distinct, and there can be no doubt that the coral is a compound fungian in which some of the septa are cribriform. The coral resembles the Jurassic Aobya, which, as shown by Kobya crassolamellata, Gregory (1900, pl. xxiii, fig. 2c), has the same fascicular columella and alternation of solid and cribriform septa; but in the Jurassic Kobya the trabecular structure of the septa is more regularly developed.
488 J. W. Gregory & Jean B. Trench—Eocene Corals.
The genus Coscinarea has always appeared out of place in the Agaricioida, in which Duncan placed it; and the characters which led to its reference to that alliance appear to be unessential features due to habit of growth. The characters of the septa show that Coscinarea is allied to the Jurassic genus Aobya. Owing to the kindness of Professor Stanley Gardiner we have been able to examine a series of specimens of Coscinarea, including some of the type species of the genus. Coscinarea appears to us to be a descendant of Kobya, in which the corallum, instead of being massive, is an encrusting lamina, and in which the corallites tend to occur in short series separated by raised bands that have sometimes the aspect of collines. The columella is small and deep.
In Kobya the corallum is massive, the calices are separated by flat surfaces traversed by septocoste, the columella is large and, though parietal in structure, it may end above as a single papilla. The species of Kobya which most closely approaches Coscinarea is K. lenticulata (Gregory, 1900, p. 172, ‘pl. xxii, figs. 8, 4), in which the corallum is flat and lenticular. Tis corallites tend to grow in concentric series with slightly raised edges ; its corallum is, however, massive, and this species only indicates a tendency towards the characters of Coscinarea. That genus is one of the distinctive corals of the Indian Ocean and Red Sea, and the occurrence of Kobya in Bathonian and Eocene times in the same region is geographically consistent with the suggested relationship between the two genera.
C. andrewst, the Miocene species from Christmas Island, was described as ‘‘apparently massive’’. It will therefore probably be found, when better specimens of it are available, to be a Hobya. It differs specifically from KX. hemicribriformis in that the corallites are much smaller; in the Christmas Island species the corallites are only 10mm. and the columella 2mm. in diameter, whereas in KX. hemi- cribriformis they are respectively 15 and 3 mm. in diameter.
EXPLANATION OF PLATES. PLATE XIX.
1. Stylina macgregori, n.sp. No. 27. Fig. la, part of upper surface of , corallum, x 3 diam.; Fig. 16, part of polished surface of same specimen, horizontal section, x 3 diam. 2. Leptoria carnei, n.sp. No. 6. Part of polished surface of corallum, x 3 diam. 3. L. carnei,n.sp. No. 7. Part of polished surface of corallum, x 3 diam.
PLATE XX.
1. Plesiastrea horizontalis, n.sp. No.18. Fig. la, part of polished surface of corallum, vertical section, X 3 diam.; Fig. 1b, part of polished surface of same specimen, horizontal section, x 3 diam.
2. Dachiardia macgregori, n.sp. No. 5. Fig. 2a, part of corallum showing a few corallites and granular surface, x 2 diam.; Fig. 26, part of polished surface of same specimen, X 2 diam.
3. errors papuensis: n.sp. No. 22. Part of surface of corallum,
% diam.
(To be concluded in our next Number.)
‘Hon. Maa., 1916. PEATE XX
Photos by S. Fingland. Gregory & Trench.
EOCENE CORALS, NEW GUINEA.
Stylina. Leptoria,
. eae + “i 7 5 i ‘
Photos by S. Fingland. Gregory & Trench.
KOCENE CORALS, NEW GUINEA. Plesiastrea. Dachiardia. Stylophora.
Dr. Du Riche Preller—Ophiolithic Rocks, E. Liguria. 489
IJ.—Tue Opniortitaic Grovurs oF rHE LicuRIAN APENNINES. Il. Easrern Liguria. By C. S. Du RICHE PRELLER, M.A., Ph.D., M.I.H.E., F.G.S., F.R.S.E.
GENERAL FEATURES.
fJ\HE three principal ophiolithic groups of this region are those of
Levanto, Monte Bianco, and Monte Penna, about midway between Spezia and Genoa, viz. north of Levanto, Sestri Levante, and Chiavari, at average altitudes of 300, 800, and 1,600 metres respectively. Like the Eocene ophiolithic group of Sestri Ponente and Isoverde, west of Genoa, they lie in the upper horizon of that formation, that is, in the fossiliferous (fucoids) albarese limestones and the argillaceous schists which rest on the Middle Eocene macigno sandstone as the lowest member of the Ligurian Eocene. The sedimentary and infolded ophiolithic groups consecutively aligned from the coast to the crest of the Apennines form a series of anti- clines north to south, dipping west, with some transverse folds. The whole region is greatly contorted and brecciated; it is, moreover, profoundly eroded by torrents charged with calcium carbonate which has accelerated erosion and at the same time re-cemented breccia. Although the three groups are now separated, they are, together with the scattered islands north of the crest of the Apennines towards Piacenza in the Po Valley, only the remnants ofan originally continuous formation of no less than 1,500 square kilometres or 600 square miles.
The principal ophiolithic rocks of the three groups are serpentine, euphodite, and diabase, with their varieties. The serpentine is both compact and schistose, and often of porphyric structure. There is no passage from serpentine to the other two rocks, but there are frequent transitions between the latter; serpentinous schist or pseudo- serpentine, often in transition to argillaceous schist, is also much in evidence. Associated rocks are the semi-crystalline schists known as flaniti and diaspri, viz. silico-caleareous, reddish and green schists, harder than limestone, indurated by taking up silica at the expense of lime, and containing radiolaria. Both, and notably the more highly ‘indurated diaspri, form bands on the margin of ophiolithic rocks in proximity to calcareous masses.! It is a noteworthy feature that metalliferous deposits are found only in euphodite and diabase, never in serpentine, though often near the contact of the latter; again, manganese occurs, not in the ophiolithic rocks proper, but in the diaspri masses, though in the vicinity of the former.
I. THe Levanto Group. (Figs. 1 and 5.)
This extends along the coast from Monterosso to Levanto, Bonassola, and Framura for about 10 kilometres, and inland about 20 kilometres to north of La Baracca on the high-road from Sestri Levante to Spezia. ‘The precipitous, craggy outcrops along the coast are composed chiefly of greenish and dark reddish serpentine and of
1 Indurated, silico-argillaceous schists are known as galestri, yellowish, red,
or green in colour; ardesia are tegular, silico-argillaceous-caleareous schists ; and resinite is a white or yellowish siliceous, semi-opaline variety.
490 Dr. Du Riche Preller—Ophiolithic Rocks, HE. Liguria.
euphodite alternating with argillaceous schist all more or less decomposed, except the euphodite with felspathic base and smarag- dite of Bonassola, which, though it exhibits secondary minerals, is comparatively fresh.’ The principal outcrops inland are exposed along the road from Levanto to La Baracca (600 m.), where the ophiolithic series may be conveniently studied in the numerous quarries of the beautiful and well-known ‘‘ green marble of Levanto ” largely used for ornamental purposes. It is essentially compact serpentine, greenish and rusty red, with clear white veins which are fissures filled with calcite. ‘The rock passes to a more crushed and brecciated variety, re-cemented by calcium carbonate as ophicalce. Another variety is the so-called ranochiaia or frog-coloured, which in a greenish yellow groundmass exhibits fine, black, arborescent tissues of opacite. The compact serpentine also passes to schistose, fibrous, and steatitic, is often spheroidal, and, when it contains enstatite, diopside, bronzite, and notably diallage, is porphyric in structure. Along the same road serpentine often alternates with euphodite more or less altered, and with intermediate strips of pseudo-serpentine. The ophiolithic rocks are normally intercalated between argillaceous schists as the lower, and limestones as the upper strata, with occasional intervening claret-coloured diaspri. North of the Sestri and Spezia road occurs the cluster of serpentine and euphodite masses of Tavarone between Castiglione and Maissana, of Velva, Carro, Baracchino, and Matterana (Bracco), in all of which the euphodite is largely gneissiform and, notably north of La Baracea, forms a con- siderable area. Another interesting mass is that near Pignone, about 10km. east of Levanto and the same distance north of Spezia, which constitutes, in the Eocene strata, a band of about 8 by 1 km. of serpentine and euphodite, like those of the Levanto group.” It runs north-west to south-east, parallel to the latter and to the coast towards the Cretaceous, Liassic, and Rhetian strata of the Porto Venere or western arm of Spezia Bay, and forms the link between the ophiolithic groups of Eastern Liguria and those 15 km. further east of Sarzana, Lunigiana, and Garfagnana in the Magra and upper Serchio Valleys along the northern margin of the Apuan Alps.
II. Tue Monte Branco Grove. (Figs. 1-4 and 6.)
This ophiolithic and remarkably metalliferous area is situated north-west of the Levanto group; its lower end, touching the Sestri and Spezia road near Bracco (448 m.), lies about 6 kilometres north of the former town. It covers about 10 by 5 kilometres, and is crossed north-east to south-west by the deeply eroded ravines of the Graveglia, Gromolo, and Petronia torrents in its northern, middle, and southern part respectively. It is traversed north to south by three more or less parallel ridges, viz. anticlinal folds dipping west, the highest
1 Some of the rocks near Levanto. were described by Professor Bonney in op, cit., GEOL. MAG., 1879, p. 362 et seq.
2 Specimens of the Pignone group were examined microscopically by Professor A. Cossa of Turin, who also gives analyses of the same in comparison with some of the similar Ligurian and Tuscan rocks (Boll. R. Com. geol., 1881, p. 246 et seq.).
Dr. Dw Riche Preller—Ophiolithic Rocks, EH. Inguria. 491
Sketch Map of Ophiliothic Groups, Eastern Liguria
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492 Dr. Du Riche Preller—Ophiolithre Rocks, E. Liguria.
Sketch Map of Ophiolithic Groups, Eastern Liguria.
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Fig. 5. Levanto Group. Fig. 6. Monte Bianco Group.
Fig. 7. Monte Penna Group.
Dr. Du Riche Preller—Ophiolithie Rocks, E. Liguria. 493
or eastern of which includes Mte. Porcile (1,249 m.), Zenone (1,072 m.), Alpe (1,096 m.), and Pu (1,007 m.), while the middle one comprises Mte. Bianco (876 m.), Rocca Grande (968 m.), Mte. Treggin (876 m.), and Mte. Loreto (360 m.), and the western descends to 400 and 300 m. altitude.
The ophiolithic rocks are infolded in the usual Kocene sedimentary strata, notably fine-grained, bluish-white, nodulous, and banded limestone, and argillaceous schists, frequently tilted almost vertically. Serpentines predominate more especially in the eastern, diabase and euphodite in the western and central part; their proportion may be roughly estimated as being 2/5, 2/5, and 1/5 respectively. The northern margin of the group is, between the ophiolithic rocks on one side and the calcareous rocks on the other, fringed by bands of claret-coloured diaspri up to one kilometre in width, which crop out on some of the highest points of the middle and eastern ridges such as Mte. Bianco, Rocca Grande, Mte. Treggin, Porcile, and Alpe. The principal roads leading from the coast up into the hills are those from Sestri to Casarza and Castiglione (271 m.) along the Petronia Valley in the southern, and from Lavagna along the Graveglia Valley to Nascio (390 m.) in the northern part of the area, as also the roads up the Gromolo Valley to the Libiola mine (380 m.), and from Casarza to Bargone in the centre of the area. The first of these more especially crosses in succession the serpentine, diabase, and euphodite masses in a natural section west to east of about 4 kilometres, along the Petronia Valley between Casarza and Castiglione. This section is very similar to a larger, parallel one across the widest and central part of the group from the Gromolo Valley to Rocca dell’ Aquila,
‘ Rocea Grande, and Monte Zenone, cutting the three anticlinal folds and the synclines between them. ‘These sections and another interesting one along the Libiola road, showing nodulous diabase, and euphodite veins in serpentine, are represented in Figs. 2, 3, and
- 4.1 Throughout these sections the euphoditic masses more than the other rocks are greatly altered, and often decomposed; the contact with serpentine is always distinct, while euphodite and diabase constantly merge into each other.
The euphoditic and diabasic masses throughout the area contain considerable nodules of copper pyrites which are worked in a number of mines, some of whose approach-tunnels afford interesting exposures. One of these is notably the Libiola mine above the hamlet of that name and in the Gromola Valley on the western margin of the area at about 350 metres altitude, in a diabasic island of a serpentine mass. The green and reddish diabase here is not only compact but forms laccolitic aggregations in which nodules of pyrite are embedded and separated from the encasing rock by thin strips of white resinite. In another mine on the left of the Gromolo torrent nodulous euphodite appears encased in serpentine, which is completely altered to steatite. - Manganese is found only in the diaspri bands, while serpentine throughout is devoid of metalliferous deposits, as previously stated, though they often appear in close proximity to it.
1 These sections are deduced from LL. Mazzuoli’s in ‘‘ Formazioni ofiolitiche della Riviera di Levante, Liguria’’: Boll. R. Com. geol., 1892, p. 2 et seq.
494 Dr. Du Riche Preller—Ophiolithice Rocks, EL. Liguria.
It was urged at one time as a remarkable phenomenon that in Eastern Liguria serpentine always appears superposed on euphodite and diabase, whereas in other parts of Italy, e.g. in Tuscany, the reverse is the case.’ The former phenomenon is, however, apparent rather than real, being due not only to the effects of erosion which sometimes. expose the outcrops at abnormal levels, but more especially to faults and inverted folds in connexion with the greatly disturbed stratigraphical condition of the whole region. Of this condition a striking example is afforded in the very centre of the area by Monte Treggin (870 m.), a sharply pointed, rugged peak, which is not only surrounded by chaotic masses of breccia and rock-débris, but is itself a confused agglomeration of the ophiolithic and sedimentary rocks of the area, strangely brecciated, crushed, intermixed, and contorted. This — phenomenally disturbed condition extends from Mte. Treggin north to the serpentine mass of Mte. Bocco (1,027 m.), and south to the ophiolithic masses near Bargone and Mte. Loreto across the Bargonasco and Petronia Valleys; it constitutes, in fact, an eminently cataclastic zone which runs north to south midway of the area and also from La Baracca along the western margin of the Levanto group down to the coast near Bonassola.
III. Tar Monte Penna Grove. (Figs. 1 and 7.)
This extensive ophiolithic area, the most northern of the three groups, lies north of Chiavari, whence Monte Penna, the highest point of the Ligurian Apennines (1,735 m.), forms a conspicuous object, distant about 25 kilometres. The group comprises a series of mountains disposed, on the crest of the Apennines, in a semicircle facing west and about 15 kilometres in length. In the centre of this semicircle, at 550 metres altitude, or nearly 1,200 metres below the crest, lies the village of Prato, one of a cluster of hamlets called Sopra la Croce, which possesses a mineral spring. About 900 metres above Prato, on Prato Molle, rises the Penna torrent, which, together with its numerous affluents, collects the drainage of the southern watershed of the Monte Penna group and discharges into the Sturla torrent at Borzonasca (160 m.). This village, about 15 kilometres from Chiavari, is the starting-point for the western and central part of the group, while the eastern part and Mte. Penna itself are also reached from 8. Maria del Taro (700m.). From west to east the group comprises Mte. Ajona, Cantomoro, Nero, Penna, Scaletta, Rocchetta, Pertusio, and Ghiffi, with the western lower spurs of Mte. Agugiaia, Campo Rondio, Mte. Bregaceto, and Mte. delle Lame, while Rocca Borzone forms a spur at the eastern extremity.
The ophiolithic rocks, chiefly composed of peridotite, lherzolite, serpentine, diabase, and their breccia, are, like those of the Levanto and Monte Bianco groups, infolded in Eocene argillaceous schists, limestone, and sandstone, and follow, with the latter, the same general direction north to south, dipping west, although the folds and alterna- tions of both series are often so brecciated as to defy delimination. Between Borzonasca and Prato the sedimentary strata give place in
1 See an earlier memoir by L. Mazzuoli & A. Issel, ‘‘ Studi sulle masse ofiolitiche della Riviera di Levante’’: ibid., 1881, p. 313 et seq.
- Dr. Du Riche Pretler—Ophiolithic Rocks, E. Liguria. 495
the upper part to brecciated limestone and diabase, whose repeated alternations are followed by a mass of diaspri wedged between diabasic breccia, and then by large masses of spheroidal diabase. From Prato, which lies in normal sedimentary strata, to Mte. Agugiaia (1,088 m.) the outcrops again disclose brecciated alternations with spheroidal and variolitic diabase, then a large mass of reddish bastitic peridotite which forms the cupola of Campo Rondio, and is surrounded by diabase and an outer fringe of argillaceous schist. Diabase is again in evidence on Mte. Bregaceto (1,171 m.) and extends to Mte. delle Lame (1,804 m.), which, though covered with plantation, exhibits that rock on its lower flanks.
From Mte. delle Lame the crest is reached on Mte. Ajona (1,692 m.), on whose comparatively broad and flat surface appears a very hard, dark-red, and rusty-coloured peridotitic rock in superposed layers like flagstones, with reticular ribs and wrinkles evidently due to atmo- spheric denudation. This rock, which is strongly magnetic and extends considerably north of the crest, obviously passes to serpentine on the southern flank, where serpentinous and limestone breccia appear infolded in argillaceous schist. ‘The crest of Mte. Nero towards south~- east of Mte. Ajona exhibits the same peridotitic rock passing to serpentine, and so does the remarkable outcrop of Pria Borgheise, a boss on Prato Molle (1,496 m.), below Mte. Nero, which was first noticed by Mazzuoli and, thanks to Professor Cossa’s microscopic examination, was recognized as the first example of lherzolite in the Ligurian Apennines. East of Mte. Ajona rise Mte. Cantomoro and the peak of Mte. Penna, both composed of diabase, which also applies to Mte. Scaletta south-west of Mte. Penna. These three mountains obviously form a central mass of diabase between the peridotitic and serpentinous masses on the west and those of Mte. Pertusio on the east. Mte. Scaletta and Mte. Pertusio are separated by the argillaceous schist and limestone breccia of Mte. Rocchetta. ‘The semicircular - group is completed by Mte. Ghiffi, on whose northern flank appear limestone and breccia, the contact of these rocks and the serpentine of Mte. Pertusio being exposed in the saddle between the two mountains. On the descent from here by Rocca Borzone the hard diabasic breccia with associated diaspri appear again, being evidently connected with those already noticed above Prato. A notable feature of the Mte. Penna group is the absence of superficial outcrops of euphodite, though that rock probably occurs in places below the surface where the latter is covered with vegetation or detritus, in association with diabase and serpentine as it does in the other ophio- lithic areas of Eastern Liguria. North of the Mte. Penna group, about a dozen ophiolithic, chiefly serpentinous, islands crop out in the Trebbia, Aveto, and Nure Valleys, near Bobbio, 8S. Stefano, and Ferriere respectively, towards Piacenza in the Po Valley; they are obviously a continuation of the Ligurian groups.’ The diabasic masses
1 J. Mazzuoli, ‘‘ Formazione ofiolitica nella Valle del Penna’’: Boll. R. Com. geol., 1884, p. 384 et seq. A. Cossa, ‘‘ Intorno ad alcune roccie della Valle del Penna nell’Apennino ligure’’: Rendiconti R. Accad. Lincei, Roma, 1886, pp. 502 and 643 et seq. Professor Cossa, of Turin, also first examined
496 Dr. J. Allan Thomson—On the Terebratellide.
of Mte. Cantomoro, Penna, and Scaletta extend south-east, towards Varese-Ligure, to Mte. Quatese, Cavallone, Setterano, and Carignone, all at about 1,300 metres altitude, in three more or less parallel zones with intervening strata of argillaceous schist containing abundant lenticular intercalations of diabasic breccia, of which extensive agglomerations also appear on the northern flanks of Mte. Penna. The diabasic zones obviously represent original submarine lava streams flowing in the planes of the plastic sedimentary strata in which the débris became infolded and cemented to breccia.
ConcLusion.
The phenomena presented by the ophiolithic and sedimentary groups of Eastern Liguria are substantially the same as those of the Triassic Voltri and the Sestri and Isoverde Eocene groups west of Genoa. Both regions afford striking evidence of intense folding, crushing, contortion, and brecciation which the sedimentary and the ophiolithic rocks of submarine eruptive origin during their contemporaneous uprise and subsequent settling experienced alike. There is no tangible evidence of these groups being transported areas, while everything points to their emergence and location in situ.! The effects of repeated earth-movements, including those of a seismic character, are strikingly evidenced by the frequently cataclastic condition of the Ligurian littoral from the coast to the crest of the Apennines, and the compression of the region during its uprise and settlement must have been all the greater considering that it lies in the contracted semicircular curve of the Gulf of Genoa.
III.—On tae CrasstFicatTion oF THE J'EREBRATELLID®.
By J. ALLAN THomson, M.A., D.Sc., F.G.S., Director of the Dominion Museum, Wellington, New Zealand.
Inrropuctron.
\HE observations presented by Mr. J. Wilfrid Jackson (1916) ? on my paper on ‘‘ Brachiopod Morphology”, published in this Magazine in 1915, are very welcome as furnishing many important details omitted by Davidson and other writers in the description of species. The error into which I fell as regards the types of folding of Dallina and Dalinella illustrates the danger of relying on figures when specimens are not available, but it was worth while making such an error when the correction of it brought forward so many useful observations on other points, particularly on the prevalence of
microscopically some of the ophiolithic rocks on the north of the Apennines : “Sopra alcune roccie serpentinose dell’Apennino Bobbiese,’’ Boll. R. Com. geol., 1881, p. 58 et seq. ; also D. Zaccagna, Relazione, 1902; ibid., 1903, p. 39.
' Further east towards Spezia the Mesozoic and Tertiary sedimentary strata exhibit an abnormal superposition which has always been regarded as an extensive inverted fold, but may be the effect of an overthrust. In the ophiolithie areas of Eastern Liguria, on the other hand, the Hocene sedimentary sequence is normal.
2 References are given in the list of papers at the end of this article, and are indicated in the text by the author’s name and date.
=
Dr. J. Allan Thomson—On the Terebratellidcee. 497
dental plates in the Dallinine and the relationships of Miuhifeldtia. These observations pave the way for a further advance in the natural or genetic grouping of species and genera. At the same time, while admitting that Dallina is ventrally biplicate, I am not disposed to agree with Mr. Jackson that the folding is exactly comparable to the ventral biplication exhibited in some species of MMagellania, but probably arose in a different way. I refrain from a further statement on this point, as I understand that Mr. 8. S. Buckman is discussing the subject of types of folding fully in his forthcoming memoir on the Jurassic Brachiopods of Burma. In what follows I shall have again, through lack of specimens in Colonial museums, to rely on figures to some extent, and may possibly again err from this cause, and if so hope the correction will be applied as promptly and informatively as in the former case.
Primary Divisions oF THE TEREBRATELLIDS.
Beecher, in 1895, recognized three subfamilies within the Terebratellide, distinguished by loop characters and development, viz.: the Megathyrine, the Dallinine, and the Magellanine. In 1897 Schuchert included besides these three also the Devonian Tropidoleptine, but in 1913 he relegated this subfamily to the Strophomenide, with the other members of which it agrees more nearly in geological age, and retained in the Terebratellide only the three subfamilies adopted by Beecher, whose epoch-making classification has thus stood the test of time for twenty-one years.
Certain minor modifications of Beecher’s statement of the order of loop development in the higher subfamilies of the Dallinine and
Magellanine have become necessary owing to the re-naming and
closer definition of some of the genera on which he based his terms. The following table shows the former and the revised nomenclature :—
STAGES OF LOOP DEVELOPMENT IN TEREBRATELLIDS.
DALLININE. MAGELLANINE. Revised Revised Beeeher,-1895. Nomenclature. Beecher, 1895. Nomenclature. Bouchardiform Preandee Platidiform. Platidiform. Megerliniform eae Ora Ismeniform. Ismeniform. Magadiform. Magadiniform. Mihlfeldtiform. Frenuliniform. Magaselliform. Magelliform. Terebrataliform. Terebrataliform. | Terebratelliform. | Terebratelliform. Dalliniform. Dalliniform. Magellaniform. Magellaniform.
The reasons for an alteration of the terms applied to early stages of Terebratella and Magellania have been fully explained in former papers (Thomson, 1915, Nos. 2 and 3). The substitution of ‘Frenuliniform ’ for ‘Mihlfeldtiform’ has been proposed by Jackson (1916) on the ground that Mihifeldtia belongs to the Magellanine and not to the Dallinine. In any case ‘F renuliniform’ is the
DECADE VI.—VOL. II.—NoO. XI. 32
498 Dr. J. Allan Thomson—On the Terebratellide.
preferable term, since Beecher had really Prenulina sanguinolenta' in mind when he spoke of WMiihlfeldtia, for although he mentioned IM, truncata he used in his illustrations I. sanguinea = Frenulina sanguinolenta.
The so-called ‘ Platidiform’ stage of the loop in the Dallinine is not strictly comparable to the brachidium of Platidia, as is shown below, and does not appear to be represented in the adult brachidium of any known genus, but it can hardly be doubted that a genus with such characters will one day be found.
Jackson’s reasons for removing DMiuhlfeldtia truneata from the Dallinine and placing it in the Magellanine are the absence of dental plates, the resemblance of one of its early loop stages to an early loop stage of Terebratella dorsata, and the appearance of the secondary loop before the appearance of the primary lamelle. Deslongchamps showed clearly in 1884 that the young loop stages of Megerhia truncata (= Mihifeldtva truncata) form a close parallel with the adult brachidia of Kraussina and Megerlina, and it is somewhat remarkable that Beecher overlooked this resemblance and did not suspect the generic distinctness of ‘‘ Miihifeldtia truncata” and ‘‘ Mihlfeldtia sanguinea”
DIFFERENCES BETWEEN DatiiniFoRM AND MaAGELLANIFORM OnroGENY.
Before discussing whether Dihlfeldtia may be admitted into the Magellanine, it is desirable to analyse the difference in loop development between that family and the Dallinine. Beecher pointed out that in the lower genera the median septum is generally low in the Dallinine and projecting above the loop in the Magellanine. In Bouchardia, Magas, and Magadina it almost touches the opposite valve. In the young growth stages of the higher genera this difference between the subfamilies is not so marked, for the early platidiform stages of Macandrevia show a high septum. It remains true, however, that a high septum persists longer in the Magellanine than in the Dallinine. There is also aslight difference in the form of the septum, which is more elongate and board-like in the Magellanine.
In both subfamilies the secondary part of the loop appears first as a small hood? on the septum, with the opening upwards and forwards. In the Magellanine this hood is confined to the posterior, slightly lower, end of the septum, but in the Dallinine it projects further forwards. At this stage there is an important difference, emphasized by Jackson, viz., that in the Dallinine the primary loop is complete from the crural bases to the septum, whereas in the Magellanine it is imperfect. It does not appear to be yet known whether the
1 Anomia sanguinea, Chemnitz, being polynomial, Gmelin’s name must be used for this species as Dall has suggested. Beecher’s illustrations are based on those of Deslongchamps (1884), who referred to it as Terebratella sanguinea. It is, of course, a different species from Terebratella sanguinea, Leach, which was known. at that date as Terebratella cruenta.
2 The earliest stage of Terebratella dorsata described by Fischer and Oehlert (1892), which shows the secondary loop, has a ring on the septum, but I have detected an earlier stage with a hood in 7’. rwbicunda (Thomson, 1915, No. 3).
Dr. J. Allan Thomson—On the Terebratellide. 499
growth of the primary lamelle in the Dallinine commences both from the septum and the crura, as is the case in the Magellanine, or from the crura only. In the Magellanine the completion of the primary lamelle is attained only after the hood has developed into a ring, and on its completion the Magadiniform stage is reached. In this stage the primary lamelle and the ends of the ring are separately attached to the septum, and at a considerable vertical distance apart. In Platidia, as figured by Fischer & Oehlert (1891), the same is true, but in the earliest known Platidiform stages of Macandrevia and Dallina the attachment of the primary lamelle is very oblique, and the anterior part unites with the end of the hood. A similar oblique attachment and union is not attained in Zerebratella till a later stage, the Magelliform, when the ring has attained a considerable size and is widely open. ‘
Some similarity exists between late Platidiform and Ismeniform stages of Macandrevia and Daliina on the one hand and early Magelli- form stages of Zerebratella on the other. In all of these the primary lamelle are complete, and run forward obliquely up the septum to unite with a ring above. The differences are that in the Platidiform and Ismeniform stages the ring is not so large nor so widely open, while its lower ends project forwards into two divergent points, whereas in MMagella and in Magelliform stages the lower ends are more or less rounded. ;
The chief difference in later stages is that in the Dallinine lacune open on the lower sides of the ring and so produce a Frenuliniform stage which has no counterpart in the ontogeny of Zerebratella or . Magellania.
MGHLFELDTIA AND ITs ALLIES.
Mihifeldtia truncata differs in its ontogeny from members of Dallining in that the secondary part of the loop appears as a ring before the primary lamelle appear. Furthermore, as in the Magel- lanine the primary lamelle grow from each end to unite in the middle. There appear, however, to be other features in which differences from the Magellanine exist, and some resemblance to Dalliniform ontogeny may be traced. The high board-like septum of the early stages of the Magellanine does not appear to exist so far as one may judge from the figures of Deslongchamps (1884) and Fischer & Oehlert (1891). Certainly in Kraussina and Megerlina the septum is quite low. The ring above the septum in the earliest; known stages of Miihifeldtia is different in shape and position from the ring in pre-Magadiniform and Magadiniform stages of Terebratella. It lies further forward on the septum, and the lower sides exhibit forward extensions not shown in the early stages of Terebratella. At alater stagein I. trun- cata, and in the adult brachidium of MMegerlina Lamarckiana, small points which represent the anterior beginnings of the primary lamelle appear, not on the septum, but on the lower outer sides of the ring, if Deslongchamps’ figures may be trusted. This difference both from the Dallinine and the Magellanine appears sufficiently fundamental to necessitate the recognition of a subfamily to include Mihlfeldtia, Megerlina, and Kraussina. Before such a step is taken,
500 Dr. J. Allan Thomson—On the Terebratellide.
however, it is desirable that a further study of the young stages of Mihifeldtia should be made. Had Deslongchamps presented side views of the specimens he figured, all ambiguity would have been avoided.
In its further development J. truncata diverges greatly from the Terebratelliform ontogenetic series. Apparently what in the adult loop resembles the jugal band of a Zerebratella is really the original bottom part of the primitive ring, little modified except in size. The anterior extensions of the ring become greatly enlarged, and with them the primary lamelle increase in length, although remaining attached to the lower sides of the ring at their point of origin. Neither Davidson, Deslongchamps (1884), nor Fischer & Oehlert (1891) show in their figures any sign of lacune such as occur in Frenulina, but in a specimen from the Mediterranean in the Dominion Museum, Wellington, they exist as narrow slits separating for some distance the anterior extensions of the primary lamelle from the anterior extensions of the ring.
There is another genus which by an anterior extension of the secondary part of the loop prevents some resemblance to Dihlfeldtia, viz. Campages, Hedley (1905), which occurs on the south and east coast of Australia. In the type species, C. furcifera, Hedley, there is also a slight development of lateral lacune, but these do not appear to bepresent in the only other known species, C. yaffaensis (Blochmann).* Through the kindness of Dr. J. C. Verco, of Adelaide, I have been able to examine a small series of the young of the latter species. In these the typical high septum of the Magadiniform and pre- Magadiniform stages of Zerebratella is seen, and up to the Magadini- form stage there is no marked difference from the young of Terebratella except that the ribbon of the ring is broader and extends further forward. The later stages are not well displayed by the series, but it is evident, from the occurrence of a Magadiniform stage with widely separate attachment of the primary lamelle and of the ring on a high septum, that Campages is not a close ally of Mihifeldtia but an undoubted member of the Magellanine, with a loop representing a specialized development of the Magelliform stage.
There are two other species that should be considered in this connexion, viz. Megerlia Willemoest, Davidson, and TZerebratella fur- culifera, Tate. The former is a recent species obtained by the Challenger Expedition off T'wofold Bay, New South Wales, and has a loop resembling that of an early Terebratelliform stage of Zere- bratella, except that the reflected part of the loop is attached to the septum by two descending lamelle, thus enclosing a triangular space. In 7. furculifera, Tate, an Australian Tertiary fossil, the same kind of connexion with the septum occurs, but the brachidium appears to be rather more advanced, and comparable to a late Terebratelliform stage. These two species occur in the same region and are thus probably related. Their loop characters are quite distinct from those
1 Originally described by Blochmann (1910) as Magasella jaffaensis and ascribed to Campages by Hedley in 1911. Hedley also considered Magellamia Joubini, Blochmann, a species of Campages, but this species appears to be correctly placed under Magellania.
| Dr. J. Allan Thomson—On the Terebratellide. 501
of Zaqueus or any other known genus, and justify the erection of a new genus.
ALDINGIA, gen. nov.!
Genotype Zerebratella furculifera, Tate.
Until the growth stages of Aldingia are known, the subfamily of the Terebratellidz to which it belongs cannot be determined, but it appears not unlikely that it passes through a Miihlfeldtiform stage in its ontogeny, and that the descending lamelle uniting on the septum are comparable to the sides of the primitive ring in Mihlfeldtia.
Genetic Stocks In THE MaGeLianin® and DaALuLininzZ.
In a former paper (1916, No. 2) I have endeavoured to show that Magellaniform loops have been produced by parallel evolution in at least three distinct stocks, each characterized by its own type of cardinalia? and beak characters. There are, doubtless, many other stocks equally worthy of generic recognition in the Magellanine, but the evidence for their separate attainment of the Magellaniform loop is not yet forthcoming.
Dallina floridana, Pourtales. Anterior-ventral view of cardinalia of dorsal valve. SR. socket ridge ; H. hinge-plates ; C. crural bases; S. septum. There is no cardinal process. Enlarged about 23 nat. size.
Thanks to Jackson’s valuable observations we are now able to recognize similar evolutionary stocks in recent Dallinine. Thus Terebratalia and Thomsonia are shown both to possess hinge-plates and a similar type of cardinalia differing markedly from that in Dallina and Macandrevia. As the type of the folding and the beak characters are also similar in Thomsoniaand Terebratalia, these genera doubtless form one evolutionary stock.
Jackson states that Dallina possesses typically Magellaniform eardinalia, but it appears useful to draw a distinction. The only
‘1 Named from Aldinga, South Australia, a notable locality for Tertiary Brachiopods.
2 This term I intended as a (Latin) neuter plural, but in my former paper it was used as a sincular noun, and I had not an opportunity to revise the proofs.
502 Dr. J. Allan Thomson—On the Terebratellide.
species to which I have access, Dallina floridana,' possesses hinge- plates excavate anteriorly, under which the septum reaches right to the umbo as in Magellania, but there is this difference, that in Dallina jfloridana the crural bases are not closely applied to the inner sides of the socket ridges, as is the case in Magellania flavescens, but run independently from the umbo, so that each hinge-plate is separable into two parts, one between the socket ridge and the crural base, the other between the crural base and the middle line over the septum. It is this distinction, so clearly marked in this species, that led me to revive the term of ‘‘ socket ridge’ for the ‘‘ buttress’’ forming the inner wall of the dental sockets. In most types of cardinalia the crural bases are firmly united with the inner sides of the socket ridges and cannot be separately distinguished, although sometimes, as in Neothyris lenticularis, even when the two are firmly united laterally a line of demarcation can be more or less traced on the upper surface. Should Dallina septigera possess the same features as D. floridana, the type of cardinalia above described may be termed the Dalliniform type. In looking for a forerunner of Dallina with Terebratelliform loop, one would require as an essential a Dalliniform type of eardinalia. This may exist in TZerebratula spitzbergenensis, Davidson, which Jackson groups with Dallina septigera and D. floridana in type of cardinalia,:-but these species appear to have distinct beak characters. In the terminology of Buckman (1916) Dallina had a mesothyrid foramen,while Zerebratula spitzbergenensis appears to have, according to Davidson's figures, a submesothyrid foramen. More probably the forerunner of Dailina looked for will be found in Terebratella Marie, A. Adams, or in the Italian Pliocene form Z. septata, Philippi.
In my previous paper (1916, No. 1) I suggested that the forerunner of Macandrevia with Terebratelliform loop might be looked for in Terebratula frontalis, Middendorff, but refrained from creating a genus for its reception because of ignorance of its hinge-characters. Jackson states that it possesses somewhat obscure dental plates much as in Terebratalia, and that its loop development and cardinalia suggest relationship with the Terebrataliform stage of Macandrevia cranium. I have now secured a specimen of this species and find some further points of agreement with Macandrevia, but also some differences. Jackson, in describing the pedicle collar, mentions that it is never developed in the higher long-looped forms, in which Macandrevia is included, but stated that in some of these ‘‘there is occasionally a thickening in the umbo around the foramen assimilating a pedicle collar, but it is fused to the shell and never free anteriorly”’. In Macandrevia such a plate is well developed in old shells, and extends as far forwards as the dental plates, with the base of which it is firmly fused, giving the appearance that the dental plates and the pedicle collar form a single structure free laterally from the walls of the shell but closely applied to the floor. I have observed this feature most clearly in a new species of Jlacandrevia from the
' Two specimens presented to the Dominion Museum, Wellington, by the United States Deep-sea Dredging Expedition off the Coast of Mexico, 1869.
Dr. J. Allan Thomson—On the Terebratellide. 503
Antarctic, but it also exists in If. cranium.’ It is thus described by Dall (1895) in I. americana: ‘‘teeth strong, short, supported each by a strong buttress with a recess behind it, and in old specimens with a smooth deposit of callus on the surface of the valve between the two buttresses.”’ This type of dental plates, supported by a deposit of callus on the floor of the valve, differs from that of Hemithyris, and may be termed the Macandrevian type. Hemithyris has a true but short pedicle collar, with which the deposit of callus in Macandrevia does not appear to be homologous. The Macandrevian type of dental plates is also found in Zerebratella frontalis.
. The beak characters of Macandrevia are of an unusual type. The pedicle opening consists of two parts—a rounded foramen, which is permesothyrid in position,” opéning into an open delthyrium. In the usual course of events in Terebratellids, when the foramen has attained the mesothyrid position, the delthyrium has become closed by deltidial plates. In TZerebratula frontalis the movement of the foramen ventralwards does not appear to have gone quite so far, but the relation to the delthyrium is the same.
The cardinalia of Macandrevia are also of an unusual type. The crural bases are fused on their outer sides to the socket ridges as in Magellania, and from their inner sides two hinge-plates, excavate anteriorly, descend obliquely to the floor of the valve, and becoming fused with this unite in the middle line of the valve. Inthe Antarctic species above-mentioned, from which this description is drawn, these hinge-plates do not extend forward beyond the crural processes, and there is a raised thread-like line occupying the position of the median septum. In Macandrevia cranium, Davidson (1886) states that there
is no defined cardinal process or median septum, but that two deviating
septa commence under the umbo and extend toa little more than one- fourth the length of the valve. ‘These so-called septa are apparently anterior prolongations of hinge-plates similar to those described above. It is desirable that the ontogeny of the Macandreviform type of hinge- plates should be worked out. It bears some resemblance to that of early stages of TZerebratella rubicunda, but it seems not impossible that it is a further development from a Magellaniform type.
In Terebratula frontalis a different type of cardinalia exists. There is a small median septum situated in front of the middle of the valve, and from it a raised thread-like line extends back to the cardinalia as in Macandrevia. The crural bases cannot be traced in the cardinalia with certainty. The crura spring from the anterior inner corners of strong socket ridges, between which there isa mass of shell substance overhanging in front and embayed nearly to the umbo. The outer edges of this overhanging mass are raised into ridges, and perhaps mark the crural bases, and between these ridges and the socket ridges there are well-marked depressions on the mass. On the back of the mass is superposed a small transverse cardinal process.
1 It is figured, but not described, by Fischer & Oehlert (1891, pl. v, fig. 10 f.).
? The beak ridges are poorly defined, and it is difficult to be quite certain of their position. The foramen is certainly not of the submesothyrid type, into which most Terebratellids with lateral deltidial plates fall.
504 Dr. J. Allan Thomson—On the Terebratellide.
Terebratula frontalis cannot be placed in Zerebratalia and requires a new genus for its reception, for which I propose:
DiEstoTHyEIs, gen. nov. Genotype Terebratula frontalis, Middendorff.
Diestothyris presents many of the characters that are to be expected in a forerunner of Jacandrevia, and differs only in its type of eardinalia. It may be provisionally regarded as belonging to the same stock as Macandrevia, although not in the direct line of descent of that genus.
The above discussion shows that by taking into consideration characters of beak, hinge-teeth, and cardinalia in addition to loop characters, much may be done to arrange the recent species of the Dallinine into genetic stocks. The discussion is by no means exhaustive, and has not included the lower genera, for which a better knowledge of the Tertiary fossils of the Northern Hemisphere is desirable.
List OF PAPERS CITED.
BEECHER (C. E.). 1895. ‘‘ Revision of the Families of Loop-bearing Brachiopoda’’: Trans. Conn. Acad. Arts Sci., vol. ix, pp. 376-91, 395-9.
BLOCHMANN (F.). 1910. ‘*‘ New Brachiopods from South Australia,’ in Verco (J. C.), ‘‘The Brachiopods of South Australia’’?; Trans. Roy. Soc. S. Austral., vol. xxxiv, pp. 89-99 (ref. to pp. 92-3).
Buckman (S. S.). 1916. ‘‘Terminology for Foraminal Development in Terebratuloids (Brachiopoda) ’’: Trans. N.Z. Inst., vol. xlviii, pp. 130-2.
Dawu (W. H.). 1895. ‘‘ Scientific Results of Explorations by the U.S. Fish Commission Steamer Albatross. No. XXXIV: Report on Mollusca and Brachiopoda dredged in Deep Water, chiefly near the Hawaiian Islands, with Illustrations of hitherto unfigured Species from Northern America ”’ : Proc. U.S. Nat. Mus., vol. xvii, pp. 675-733 (ref. to p. 722).
Davipson (T.). 1886. ca Monograph of Recent Brachiopoda,’’ part i: Trans. Linn. Soc., ser. 11, Zool., vol. iv, pt. i (ref. to p. 62).
DESLONGCHAMPS (H.). 1884. ‘ Notes sur les modifications a apporter 4 la classification des Terebratulide ’’: Bull. Soc. Linne Normandie, sér. 1m, vol. viii, pp. 161-297 (ref. to pp. 200-11, pl. vii, figs. 1, 2, 3, 4, 9, 11).
FIscHER (P.) and OEHLERT (D. P.). 1891. Haxpeditions scientifiques du Travailleur et du Talisman, etc.: Brachiopodes. Paris.
— 1892. ‘‘ Mission scientifiques du Cap Horn (1882-3), Brachiopodes’’ : Bull. Soc. d’hist. nat. d’Autun, t. v, pp. 254-334.
HEDLEY (C.). 1905. ‘‘ Mollusca from One Hundred and Hleven Fathoms, east of Cape Byron, New South Wales’’: Rec. Austral. Mus., vol. vi, No. 2, pp. 41-54 (ref. to pp. 43-4, figs. 5, 6a-b).
— 1911. ‘‘Commonwealth of Australia. Department of Trade and Customs—Fisheries: Zoological Results of the Fishing Experiments carried out by F.1.8. Hndeavour, 1909-10,”’ part i (ref. to p. 114, pl. xx, figs. 41, 42). .
JACKSON (J. W.). 1916. ‘‘ Brachiopod Morphology: Notes and Comments on Dr. J. Allan Thomson’s Papers’’: GEOL. MaG., Dec. VI, Vol. III, pp. 21-6.
ScHucHERT (C.). 1897. ‘‘A Synopsis of American Fossil Brachiopoda, including Bibliography and Synonymy ’’: Bull. U.S. Geol. Surv., No. 87 (ref. to pp. 124-6).
—— 1913. ‘‘ Brachiopoda,’’ in Eastman (C. R.), Text-book of Paleontology, Soi from the German of Karl A. von Zittel, 2nd ed., vol. i (ref. to
. 404-5).
Cone PR). 1880. ‘‘On the Australian Tertiary Palliobranchs’?: Trans.
Roy. Soc. 8. Austral., vol. iii, pp. 140-69 (ref. to p. 161, pl. xi, figs. 7a-c).
hi ttn ——,-
Prof. Bonney—Crystalline Schists of the Alpune Chain. 505
THOMSON (J. A.). 1915. No.1. ‘‘Brachiopod Morphology: Types of Folding in the Terebratulacea’’: GEOL. MAG., Dec. VI, Vol. II, pp. 71-6.
—— 1915. No.2. ‘‘Brachiopod Genera: The Position of Shells with Magaselliform Loops, and of Shells with Bouchardiform Beak Characters’’ : Trans. N.Z. Inst., vol. xlvii, pp. 392-403.
—— 1915. No.3. ‘‘ Additions to the knowledge of the Recent Brachiopoda of New Zealand’’: Trans. N.Z. Inst., vol. xlvii, pp. 404-9.
1V.—Own tHE Ace oF THE ORYSTALLINE SCHISTS IN THE PIEDMONTESE AND OTHER PARTS OF THE ALPINE CHAIN.
By Professor IT. G. BONNEY, Se.D., F.R.S.
R. PRELLER’S recent contributions to this Magazine on the geology of the Piedmontese Alps prove that (1) Italian authorities have expressed widely different opinions on this subject, and (2) some of them have maintained sundry Alpine gneisses and crystalline schists to be Palzozoic or Mesozoic (often Permian or Trias) in age. I infer from these contributions that he is well acquainted with the physical geography of this region, but fail to find in them any signs of either microscopic study or independent petro- logical work. As these have led me in several cases to very different results, I shall venture to put them on record as briefly as possible. In the course of thirty-five visits I have wandered over the peaks and valleys of the Alps from the southern border of the Cottians to the Salzkammergut, paying at first much more attention to physical than petrological questions. But in 1869, when beginning to lecture on geology, I found not only (as I was already aware) that my knowledge of rocks was scanty, but also that on this subject very little trust could be given to much that had been written. So I tried, as best I could, to teach myself.! With this intention I visited many places of petrological interest in our own country and on the Continent, forming (partly by purchase) a considerable collection of rock specimens and slices. Circumstances soon directed my attention to the gneisses and crystalline schists, and from 1872 I paid more and more attention to them in my Alpine journeys, of which this was the thirteenth. In 1885 (my twenty-first journey) I began endeavouring to obtain clearer ideas about their succession, history, and relation to the ordinary stratified rocks, by running sections, sometimes up to, sometimes across the watershed of the chain, going in that year from the Lake of Lucerne to the Lago Maggiore and returning across the Great St. Bernard. In 1887 I made two other complete sections, one from Grenoble to Pinerolo across Dauphiné, the other across the Tyrol well to the east of the Brenner Pass, and since that date, till the last and thirty-fifth in 1911, each journey has kept petrological questions well in view. On looking over a list of my geological papers I see that about thirty deal with Alpine petrology, and may add that one result of these journeys has been a collection
1 Sorby, the ‘‘ Father of Microscopie Petrography ’’, had not published much on that subject before this date, David Forbes still less, and Samuel Allport was only beginning. The ordinary textbooks of geology were either of no value or misleading.
506 Prof. Bonney—Crystalline Schists of the Alpine Chain.
of rock specimens, which fills about thirty drawers, and of about 500 slices for the microscope.’
Thus, as my opinions have not been formed without the expenditure of time and trouble, I hope to be forgiven for expressing them with some confidence. Experience had already taught me, before beginning this work, that even accepted authorities might prove to be misleading, so I consulted, as is my usual practice, the ‘‘ literature of the subject” only so far as to ascertain the localities where the most conclusive evidence on the points at issue was likely to be found. For the sake of brevity I shall restrict myself to two questions, which seem to me the most important of those raised by Dr. Preller: (1) the origin of the pietre verdi, including their relation to the associated rocks, and (2) whether certain Alpine gneisses and crystalline schists are rightly regarded as Palseozoic or early Mesozoic in age.
The pietre verdi, according to the classification adopted by Dr. Preller (see p. 160 of this’volume), comprise, in addition to the hornblendic and chloritic schists which the name commonly covers, dolerites, diabases, and gabbros with all their varieties, lherzolites and serpentines, and even porphyrites. This classification, in my opinion, is open to the fundamental objection that it includes, with the pietre verdi (a series of rocks which, whatever may be their origin, have much in common), a number of others which, though to some extent related to them in mineral and chemical composition, can often be proved to be intrusions of later date. Probably this is always the case, but in a highly folded region we cannot obtain such clear evidence of it as in one which is comparatively undisturbed. Still, in many cases, we cannot doubt the intrusive character of certain dioritic rocks, and of many masses of gabbro and serpentine (altered peridotite), and we lose rather than gain in clearness of view by including these among the pietre verdi, instead of separating them as is done on most of the large-scale Alpine maps, such as those of the Swiss Geological Survey. The green schists—griiner schiefer or
_schistes vertes—of these maps, wherever I have seen them from the Viso to the Glockner, have much in common. In the field they generally exhibit a more or less ‘slabby’ aspect, and a fine-grained, schistose structure, being often well foliated and sometimes showing mineral banding. The microscope proves them to consist (in variable proportions) of hornblende (sometimes glaucophane), chlorites, felspars (a secondary albite often being rather conspicuous), iron-oxides, and perhaps quartz. They are not seldom distinctly cut? by masses of serpentine (altered peridotites) and gabbros. The latter are occasionally very fresh, but more often the felspar is replaced by ‘saussurite’ and the augite or diallage by hornblende—the well- known smaragdite-euphotide*® of the Saas-thal being the most remarkable variety. For some years I inclined to regard the griiner schiefer proper as being originally volcanic rocks—basaltic tuffs and
' Both these collections have been given to the University of Cambridge, and are in the Sedgwick Museum.
* As, of course, certain apparently older gneisses and schists may be.
* As this term, proposed by Delesse, has for long been familiar to English geologists, I do not see why Dr. Preller should call it euphodite (p. 161).
pr LA Uet
Prof. Bonney—Crystalline Schists of the Alpine Chain. 507
lava-flows—but found in process of work that there was generally
an abrupt boundary between them and the associated micaceous
schists. Only one section above Windisch Matrei* suggested a passage from the one to the other, and I should like to re-examine this as -I might have overlooked slight thrust faults. But in not a few places” one can trace the transformation of clearly intrusive diabases into quite ordinary green schists.
The above-mentioned green schists are sometimes intrusive into certain varieties of gneiss and mica-schist of dubious origin, sometimes into the great group of crystalline schists, obviously metamorphosed sediments, which exhibit almost every gradation from schists con- sisting largely of mica into quartz-schists on the one hand and (through calc-mica-schists) into saccharoidal marbles on the other. The serpentines can be found intrusive into the green schists; the gabbro into the serpentines;* occasionally also an aplitic granite cuts the green schists, but I do not know its relation to the other two intrusives. Thus, though all these rocks (except the granite) are basic and more or less green in colour, I prefer to follow the Swiss geological maps in distinguishing as schistes vertes the pressure- modified diabases, and grouping them (though only provisionally) with the above-mentioned calc-mica and associated schists.
Since I began to pay special attention to the petrology of the Alps I have not seen much of the dioritic belt which extends from near Ivrea by Biella and Andorna to the Val Sesia, near Varallo; still, I have come across it two or three times, enough to refresh my memory and give me a general idea of its characters. Its members may very well have been drawn from the same source as the schistes vertes and their associates, but they have probably consolidated under different (deeper-seated) conditions, and may thus be conveniently distinguished from them. As, however, this question does not seem to me to have any very direct bearing on the nature and origin of the schistes vertes, I shall venture to pass by it, merely remarking that I greatly doubt whether the porphyrite north of Biella can be included in the dioritic belt. That rock, which is more extensively developed in the neighbourhood of the Lago Maggiore, seems to me the western- most extension of the great zone of porphyrites, Permian in age, which are so largely developed near and to the east of the Adige in its course from Meran to Trent.
The second and most important point is the geological age of the schistes vertes and certain other schists associated with them. This, according to the authorities followed by Dr. Preller, is from Permo- Carboniferous to Trias; one division of the pietre verdi with certain mica-schists and minute gneisses belonging to the former, the other division with the cale-schists and crystalline lmestones, to the Lias—Trias.* Much apparent, but very little real, evidence is cited to support these determinations, and I do not hesitate to say, after
1 Q.J.G.S., 1889, pp. 87, 88, 108.
2 Id., 1893, pp. 94-103 ; 1894, pp. 279-84; 1903, pp. 55-6.
° Gabbro intrusive into serpentine is, of course, a very common thing. I may add that locally the schistes vertes are cut by eclogites.
* See p. 307.
508 Prof. Bonney—Crystalline Schists of the Alpine Chain.
having carefully studied not a few of the sections on which it rests, that they prove either nothing or the contrary. Time will be saved in discussing these sections by making two
statements: First that I have never succeeded in finding a shale of .
later Paleozoic or Mesozoic age converted by dynamometamorphic action into anything more than a phyllite—meaning thereby a slaty rock, which retains many traces of a sedimentary origin and in which the authigenous mica, though very abundant, can only be distinguished on microscopic examination, while that mineral in the ordinary crystalline schists of the Alps is much larger and is easily seen with the unaided eye. But a minute mica, like that of a phyllite though generally a little larger, may appear when a schist, gneiss, or granite has been crushed, and, besides this, the original mica may be reduced to small fragments. In such case the two schistose rocks may seem to be identical, but the difficulty of distinguishing them is restricted to a very narrow zone."
The other point is that in a region much affected by folding and thrust-faulting the apparent succession of a series of rocks is not only without chronological value but may be actually misleading. It has had this effect on the authorities in whom Dr. Preller trusts,as I will endeavour to show as briefly as possible. His first paper describes the ‘‘ Permian formation in the Alps of Piémont, Dauphiné, and Savoy ’’, and I happen to be acquainted with some of the sections there cited, as, for instance, those between Bourg d’Oisans and- Briancon and those to the south of the Mont Blanc range. In regard to the former I cannot venture to say how much of the great zone of non-crystalline rocks between Argentiére and Moutiers is Permian (the Carte Géologique de la France makes the whole Upper Carboniferous, with a little overlying Lower Trias), but the two sharp infolds of the former on either side of Freney on the western side of the Lautaret pass are perfectly distinct from the enclosing gneiss, and ordinary Liassic strata. rest upon both it and their denuded edges; overlying the former to beyond the Col du Lautaret, at elevations ranging from about 5,000 feet to 11,000 feet above the sea. Over this considerable area Permian and Trias are either absent or inconspicuous, at any rate till we come towards Briangon. As, however, I maintain that none of the stratified rock in this zone, whether later Paleozoic or earlier Mesozoic (which I have also examined in two or three places further north), is more metamorphosed than many grits and slates in Britain of the same geologic age, and that the Jurassic limestones do not differ appreciably from those in other parts of the Alps, I regard the exact geological position of the aforesaid deposits as unimportant. This, at least, is certain, that the Alpine rocks were affected by great earth-movements in both pre- Carboniferous and pre-Triassic times, and that the latter system was deposited on a very irregular surface, for in some places it is missing, in others it appears as that peculiar calcareous material called rauchwacké (often with gypsum), and in others as a group of ordinary stratified rocks, often limestones or dolomites. :
1 Q.J.G.S., 1884, pp. 4, 5, 21; 1889, p. 92, and remarks on rocks of the pietre verdi type at p. 98.
Prof. Bonney—Crystalline Schists of the Alpine Chain. 509
I will now notice a few sections which have been repeatedly quoted as proving the later Paleeozoic or earlier Mesozoic age of true crystalline schists.’
1. In 1881 I was informed by a Swiss Professor of Geology that the well-known conglomerate of Carboniferous age in the Waloraite near Vernayaz exhibited partial metamorphism, “mica scales, large enough to be seen with the unaided eye, having been developed in situ. After visiting the sections and examining the rocks under the microscope I had no doubt that the mica was derivative, like the . fragments of gneiss, etc.”
2. Some foreign geologists have claimed the crystalline schists on the mountains near Zermatt, on either side of that branch of the Vispthal, with their prolongation eastward to the neighbourhood of Saas, as metamorphosed rocks of early Mesozoic age. The only evidence that I have been able to find for this identification is that here and there a little strip of ordinary rauchwacké (Trias) is nipped in among normal crystalline schists, which seems to me, as will be . more fully shown in the next instance, strongly adverse to that conclusion.
8. The Val Canaria and Val Piora sections.—Here we find a group of mica-schists, often calcareous and sometimes passing into marbles, apparently infolded in rauchwacké, the most impressive section occurring in a ravine on the right bank of the Val Canaria. But I have shown this to be an impossible interpretation, if only from the fact that the rauchwacké contains abundantly fragments of the schists which are supposed to overlie it. We obtain similar evidence on the upper part of the Lukmanier Pass some seven miles to the E.N.E., as well as at a rather greater distance to the W.S.W. between the Nufenen Stock and the Gries Pass.‘
4. Another group of sections has been supposed to prove that certain staurolite and black-garnet schists (well developed near the Lago di Ritom) pass into schists in which these minerals (authigenous) occur with fairly well preserved belemnites and ossicles of crinoids. This assertion can be tested in sections on Scopi to the east of the Lukmanier Pass, between All’Acqua and the Nufenen Pass, and on the northern ascent to the Gries Pass.> In some cases the garnet- bearing mica-schist is parted by a little rauchwacké, from the fossili- ferous schist (supposed), but in others the two are in sequence. The occurrence of fossils in the latter is indubitable, but the minerals claimed as garnets and staurolites are only secondary hydrous minerals, too impure for precise identification, and their matrix is not a true schist. In fact, these sections prove nothing more than
1 The stock instance of gneisses and Jurassic limestones on the northern crags of the Jungfrau is now abandoned, so it needs no discussion.
2 GEOL. MaG., 1883, p. 507.
3 See Q.J.G. S. 4 1890, pp. 199-211; 1894, pp. 297-300. There are four marked varieties of these schists, three of which I have found in the rauchwacké and the fourth at the base of the Lias near the Lukmanier Pass, where this rock rests directly on that particular schist.
+) Q@:J.G.8., 1893, pp. 90-1.
> Q.J.G.S., 1890, pp. 213-21; 1893, pp. 90-1.
510 Prof. Bonney—Crystalline Schists of the Alpine Chain.
remarkable ignorance on the part of certain foreign geologists.! Want of space prevents me from discussing in detail the petrological statements on pp. 158-62 of this volume, so that I must be content with saying that, when work in the field is checked by study with the microscope, the lessons of nature are clearer than those of the authorities followed by Dr. Preller. That the kinds of rocks mentioned by them occur in certain districts is no doubt true, though their nomenclature is sometimes confused ? and the suggested passages of one kind into another, where I have seen them, are due to the obliteration of their earlier history by intense crushing, or are consequences of thrust-faulting. For such a thing as the ascription of the cale-schists and crystalline limestones, with one group of the pietre verdi, to the Lias—Trias, and the mica-schists and minute gneisses, with another group of the same, to the Permo-Carboniferous (p. 807), no evidence is given; the matter at issue is quietly assumed. The general succession of the crystalline schists—micaceous, calcareous, and quartzose—and certain. gneisses I do not dispute, for I sketched it out thirty years ago,* and have upheld it ever since, though, as I hope, I have obtained a clearer knowledge of the pietre verdi group and of certain of the porphyritic gneisses, which are pressure-modified intrusive granites, later in date on the whole than the aforesaid rocks, but do not, so far as I have seen in the Western and Central Alps, cut Paleozoic or later sedimentary rocks. The above-named schists are fairly abundant on both sides of the Pennines, especially the northern, as in the mountain region around Saas, Zermatt, Arolla, and Zinal, also in the Lepontine, Rhetian, and Central Tyrol Alps; in fact, I have examined them in many places from the Viso to the Gross Glockner—quartz-schists, cale-schists, and mica-schists. These rocks form long continuous zones, in which ‘ green schists’ appear intermittently, and overlie a variety of coarser and stronger mica-schists and gneisses, below which are large masses of granitoid rocks, which, though apparently the older, are, in many cases at least, certainly the newer. But there is nothing to prove that the schists are of Trias— Lias age, only that here and there little strips, sometimes only a few yards in length and feet in breadth, are wedged in among the gneisses or crystalline schists. No one accustomed to the last-named group of rocks would have dreamt for a moment that the friable unaltered rauchwacké could possibly form part of one and the same series with
1 Grou. MAG., 1901, p. 161.
2 For instance, the schistes lwstrées have been for long a ‘‘ waiting-room ”’ where rocks in very different states of metamorphism are left till called for.
* Q.J.G.S., 1886, Proc., p. 79. A generally similar succession of crystalline schists (originally sediments) occurs in the Highland zone between Dunkeld and Braemar, and hornblende schists (griiner schiefer of the coarser type) in the North-West Highlands. Id., pp. 91, 92.
_ 4 Papers dealing with different points in the nature and succession of these
rocks will be found in Min. Mag., 1887, pp. 1, 191; Gon. MaG., 1887, p. 573; 1889, p. 488; 1890, p. 533; 1893, p. 204; 1894, p. 114; 1896, p. 400; 1897, p. 110; Phil. Mag., 1892, p. 237; and Q.J.G.S., 1889, p. 67; 1890, p. 187; 1893, pp. 89, 94, 104; 1894, pp. 279, 285; 1897, p. 16; 1898, p. 357; 1903, p. 55; 1905, p. 690; 1908, p. 152.
ce
Notices of Memowrs—Discussion on Coal. Sint
them and have undergone a similar amount of heat and pressure, especially the former.
One word in conclusion. The reader of Dr. Preller’s papers will soon discover that he quotes as if they were authorities of equal value geologists who often express contradictory views. If one man says a group of rocks is late Paleozoic or early Mesozoic, and another that it is Archean, one of the two must be wrong, so hopelessly that it is no use quoting his opinion. Which of them seems to me to be right will be obvious from what I have written. This expresses opinions not lightly formed. More than thirty years ago I found the views (not of Italian geologists only) so widely discordant that I ceased to study their writings for any other purpose than finding out the position of sections supposed to be critical. From these I have been collecting evidence, by personal examination, visiting, on an average at least once in a year from 1881 to 1911, one or other important district, so as to test repeatedly the hypotheses both of myself and of others. The knowledge thus acquired emboldens me, audacious as it may seem, to express my complete dissent from those geologists who assert the existence of true schists and gneisses of Permian to Liassic age anywhere in the Alpine chain.
NOTICES OF MEMOTRS.
—_$§—_@——_<— T.—ReEport oF THE Jomnr Discusston on Coat at THE NEWCASTLE Meerine oF tHE British ASsocraTion.
MONG the more important items in the programme of Section C at Newcastle may be mentioned the discussion with the members of the Chemical Section on ‘‘ The investigation of the chemical and geological characters of coal, with a view to its most effective utilization as fuel and to the extraction of by-products’”’. The dis- cussion formed a natural and appropriate corollary to the President’s address. A desire, to abolish the present haphazard methods of utilizing coal—the natural outcome of the backward state of our knowledge of the mineral and its many varieties—was the keynote of the debate; and the desire found immediate expression in the formation of a research committee of Section C to deal with the matter, as well as in the nomination of geological members to serve on the committee of Section B dealing with Fuel Economy.
‘The discussion was most appropriately opened by Professor G. A. Lebour, who said that the geologist regards coal as a rock disposed in layers or seams sandwiched between a roof and a floor of other rocks, and subject to changes in thickness and to interruptions of continuity of various kinds. There are also changes in physical properties and composition, to investigate which he needs the help of others. It is his business to find the coal either by mapping the outcrops or, where there are none, by weighing circumstantial stratigraphical evidence of all sorts. He thus points out the possible extension of known, or the existence of hidden, coalfields. As to the composition of the coal in the seam asa whole, or in the different parts of the seam, he turns to the chemist for information. There is
512 Notices of Memoirs—British Association—
wanted an agreed classification of coals based on both physical and chemical characters. He asked help from the chemists in providing such a classification, with a clear definition of each variety. The value of the analyses provided by the chemists would be greatly enhanced, from the geological point of view, 1f they could be informed of the nature of roof and floor respectively, since both are factors which undoubtedly influence the composition and properties of the coal between them. It was also very desirable that the analyses should be presented somewhat more uniformly drawn up than is the case at present. For geological purposes an ultimate analysis is of little or no use alone, but should be given together with one of the ordinary commercial kind, in which the percentage of free carbon, volatile matter, and ash is shown. One seam in the Newcastle Coal- field yielded in the north the best household coal, in the centre of its area the best coking coal, and, further south, the best steam coal of the district. He concluded by saying that after fifty years of work at coal he knew less what it really was than he thought he knew at first.
Professor W. A. Bone said he found it difficult to make any very definite statement about the chemical nature of coal, of which we were still largely ignorant. The technical chemist was in the habit of making certain tests with a view to judging the suitability of a given coal for particular economic purposes, and the ultimate com- position of the coal substance can be determined with considerable accuracy. But such data, however useful as a guide to the user of coal, gave little or no information as to the chemical structure of coal. Within recent years a good deal of work had been done upon the action of various organic solvents, notably pyridine, upon coal, upon the results of which certain tentative conclusions had been drawn as to two different types of constituents (sometimes termed the ‘resinous’ and ‘cellulosic or humic’ types respectively) which are supposed to make up the coal substance, and this seemed to be a promising line of attack upon the problem. But it was too soon yet to put forward anything more certain than a working hypothesis. During the past thirty years a number of eminent chemists had individually attacked the problem of the chemical structure of coal on different lines, but little or nothing had been done to co-ordinate these various researches or to review their results in any active manner. In his opinion no great progress was likely to be made except on the lines of some well-considered scheme of research in which the various workers would find their place and collaborate. The Fuel Economy Committee had the matter in hand, and if the geologists wished to be more largely represented their further valued assistance would be welcomed by the chemists. _
Professor Kendall (Leeds University) addressed himself particularly to the question of the nature and origin of the ash in coal-seams, asubject of great economic and geologicalimportance. He recognized three sources of the mineral substances found in coal-seams—first, the residue of the actual mineral constituents of the plants composing the coal; second, detrital mineral matter, generally fine dust or mud, that had been blown or washed into the area of coal-formation; and
Discussion on Coal. Ss
third, the sparry snbstances, generally calcite or iron pyrites, segregated as velnsin the seams. The ordinary method of making an analysis for commercial purposes would not, of course, dis- criminate between these. A certain weight of coal was taken as nearly as possible representative of the whole seam, and after being broken into small particles was sampled and the fraction analysed. This gave no details as to the location of the respective types. of ash, observation upon the seam under ground, or of the coal as marketed, nor showed how the sparry material was disposed in the ‘cleat’ or system of joints traversing bituminous coal. The work done in Neweastle by Dr. Garrett and the late Mr. Burton, who obtained radiographs of slices of coal, promised results of great interest; other means were also available. It is well known that ordinary coal consists of alternating bright and dull layers, and the late Professor A. H. Green obtained separate analyses of these two types, showing that the bright layers yield a very low ash percentage, while the dull charcoal layers may contain a much higher proportion. This has been confirmed by general experience. Another method employed for the purpose of deciding whether a coal would be improved by washing was to crush it down to fine granules, ~4;in. in diameter, and separate by specific gravity into moieties respectively of 1:2-1°3 and 1:3-1°4. The former in cases cited proved to be bright and lustrous, and to have an ash content amounting to only one-fifth of that found in the heavier sample, which was of a dull aspect. The inference has been drawn from the very low ash content of anthracite that it was composed of a different assemblage of plants from those producing the more bituminous seams or parts of the same seam. ‘The speaker demurred to this, and pointed out that low ash is not a universal characteristic of anthracites, but also that two features of anthracite seams combined to give a low ash, the dull layers are generally of very small dimensions, and anthracite, the world over, is destitute of ‘cleat’. The contention that the sparry infilling of ‘cleat’ crevices in bituminous coal is derived from the coal, seems contradicted by its composition—the high percentage of calcium carbonate and of iron and low potash in the ash taken as a whole is the reverse of what would be found in any average assemblage of plants, and the speaker would regard the lime and the iron as introduced bp pereolation from the measures. It is much to be desired that geologists, chemists, and paleobotanists should combine to make exhaustive studies of a seam from floor to roof, and also to extend their scrutiny to the variations of a given. seam from place to place, so that such anomalies could be explained as that of a well-known seam in Yorkshire that in two adjacent pits passes from a ‘ coking’ to a ‘non-coking’ condition.
Dr. Dunn thought the discussion showed the need of co-operation and collaboration, not only of the chemical workers, as suggested by Dr. Bone, but of geologists and botanists with the chemists. Professor Lebour had blamed the chemists for not furnishing a philosophical classification of coals; but classification depended partly on the purpose to be served by it, and partly on the extent of our knowledge of the things to be classified. Such classifications as had been
DECADE VI.—VOL. I1.—NO. XI. 33
514 Notices of Memoirs—British A ssociation— .
attempted had had in view chiefly the various uses of coal, and had no pretensions to being scientific or philosophical, or indicative of the real nature of various coals; and our knowledge of that nature was so rudimentary and incomplete that no true classification was possible. Analyses of coal, too, had chiefly been made for users of coal, and the form which gave the information needed by one class of user might not be suitable for another; the geologists had hitherto for the most part been able to make use only of such analyses, and hence arose the lack of uniformity spoken of by Professor Lebour. All these analyses dealt with the products of the destruction of coal, not with the substances actually contained in it; though much work had been done in the endeavour to understand the nature of coal, very little progress had been made, and we knew little more than that coal contained two or three substances separable by different solvents, one of which seemed to be intimately connected with the coking properties of coal. The question of the ash of coal, raised by Professor Kendall, was a very important one, especially the separation of the inherent ash, or mineral matter originally contained in the plants from which the coal was derived, from the extraneous mineral matter, and also the distinction between ash irregularly distributed as ‘ dirt’, ‘stone’, or ‘shale’ among the coal, and that found minutely sub- divided throughout it. Great variations occurred in the composition of the ash; it was usually a complex mixture of silicates, but he had had one sample which was practically a pure china clay, and another which contained over 80 per cent of ferric oxide. Analyses of ash, like those of coal, were usually made by chemists who were unacquainted with the geological features of the occurrence of the coals concerned; and the problems raised by the geologist could never be enlightened by the chemist unless the whole of the circumstances were put before him, and analyses made on the geologist’s own samples and for his own purposes. To do this completely, for a survey of all the coal-seams of the kingdom, will involve an enormous amount of labour, and will need not only hearty co-operation between chemists and geologists, but financial assistance on a scale that can hardly be furnished by any other body than the nation.
Professor Bedson dealt briefly with the investigations which. had been made into the nature of the organic proximate constituents of coal. He drew attention to the reports of a committee of Section B published in the Transactions of the Association in 1894 and in 1896, and spoke of some of the more recent attempts to isolate the constituents of coal substances by the aid of solvents, amongst which pyridine and quinoline appear to be the most efficient. Although a considerable © amount of work has been done, still we are lacking exact information as to the chemical nature of the substances dissolved and the undissolved portions.
Mr. D. Trevor Jones, speaking on behalf of Dr. R. V. Wheeler and himself, and dealing with the question of the constitution of coal from the chemical aspect, remarked that coal is considered to have been formed from decayed vegetable matter by the action of pressure and temperature. The temperature must have fallen short of 300° C. The coal conglomerate can be resolved by means of solvents into
Discussion on Coal. 515
cellulosic and resinic portions. The cellulosic derivatives contain compounds the molecules of which possess the furan structure and yield phenols when destructively distilled. There are also compounds present the molecules of which have structures resembling that of the carbon molecule, but it is unlikely that ‘free’ carbon is present in coal. The cellulosic derivatives are probably few in type. The resinic derivatives contain compounds in which alkyl, naphthene, and unsaturated hydroaromatic radicles are attached to larger and more complex groupings. It is doubtful whether aromatic groupings are present. Under the influence of pressure the bulk of the resinic derivatives have become highly polymerized. The oxygenated resinic derivatives are chiefly oxides, probably cyclic oxides; esters, lactones, anhydrides, acids, and ketones are absent or present only in small quantity. Hydrocarbons exist in the resinic portion of coal; saturated hydrocarbons (paraffins) are, however, present in small quantities only.
Dr. Marie ©. Stopes, who had also been working in conjunction with Dr. Wheeler, said that in dealing with the composition of coal the chemist is faced with the difficulty that there are contained in it a number of different compounds which must be separated from one another before their characters can be determined. ‘The only clue to their composition is the fact (no longer seriously disputable) that they are of vegetable origin. In estimating the nature of coal unaltered by heat or chemical action, up to date the chemist has done no more than, by means of solvents, roughly to separate coal into two main classes of constituents which have been termed ‘cellulosic’ and ‘resinic’. Of these the ‘cellulosic’ constituents are separable into two groups. Palobotany has established the fact that some, if not all, ordinary bituminous coals are formed from a mixture of various parts of land-plants.1 No living plant is so simply divisible into two constituents as is coal into ‘cellulosic’ and ‘resinic’; cellulose forms the major part of the cell-walls of the soft tissues, resin may be present in special cells or glands, and may possibly be modified from various cell contents, but the different portions of even the simplest land-plant are composed of a great variety of distinct chemical compounds, many of which have been named and classified by plant- physiologists. Though a number of these substances may be but slight variations of the ‘cellulose’ complex molecule, yet in the living plant they have distinctive work to do and have recognizably various morphological and physical properties. It is not unnatural to assume, therefore, that these various substances may be the sources of different chemical compounds now in coal. It will be readily understood that were different by-products from coal traceable to specific parts of plants, and these plant-remains were visually recognizable in the coal itself, a considerable step might be made in our knowledge of coals and their potentialities. For the individual plant portions might be isolated by suitable methods, and the substances for which they were responsible when coal is heated determined. (This is not invalidated by the fact that these portions may or may not differ in composition from the corresponding parts of living plants.) It is on such work that we are at present engaged,
1 Though this is widely accepted it has been proved in very few cases.
516 Notices of Memoirs—British Association—
using as the starting-point the instance that the phenols obtained when coal is destructively distilled are derived from that particular class of compounds grouped as ‘cellulosic’. As plant mechanisms had evolved many distinctive forms of cellulose compounds even by the time of the Carboniferous epoch, we think it is necessary to ascertain whether the various modifications of cellulose differ materially in the compounds they yield, and if so which part of the plant substance’ corresponds to any particular coal-derivative. An illustration may be useful here: Conspicuous in the construction of many coals are the small yellow bodies known to everyone as spores. Their walls are formed of a derivative of cellulose. Are they, or are they not, still in a condition to react distinctively to treatment by pyridine ? Those who have experience in the examination of coals will recognize the practical difficulties in the way of anstvering so apparently simple a question, for hitherto spores have not been recognizable in lump coal but in thin sections, while, on the other hand, thin sections are not suitable for extraction hy pyridine. Nevertheless the difficulties have been overcome, and in the insoluble residue of coal extracted by pyridine we have observed unaltered spores in large numbers. This proves that the particular modification of cellulose forming their walls is one of the ‘cellulosic’ derivatives insoluble in pyridine. Since some coals are largely composed of spores this fact is of some value, more particularly as spores have a most distinctive appearance and are generally recognizable in thin sections. The next stage in the work is the isolation from coal of a sufficient number of spores to make possible a chemical examination to ascertain what particular type of chemical compounds they yield on destructive distillation. Spores, though the most conspicuous, are by no means © the principal constituents of most coals ; wood, soft parenchyma, cork, chlorophyll-containing or green tissues of leaves, must all have been universally present in proportions varying from inch to inch in the mass of débris from which any humic coal was formed. Cuticles, morphologically very distinctive portions of plants, and at the same time largely formed of a specific chemical compound to which the name cutin has been given, are conspicuous in the coal substance. We have now isolated sufficient pure cuticles from coal to distil them separately. It will be our business to track down the substances in coal one by one and to isolate them in such a form as will render their chemical examination possible. To hunt this extremely elusive game the microscope is necessary, and ‘the chemist alone is unable to interpret what is to be seen on its field; the palzobotanist alone cannot probe into the chemical composition of even the plant- structures he best recognizes. Thisis obviously a case for co-operation. The practical aim of such work should be to devise methods whereby satisfactory evidence can be obtained as to the most economic use to which a given seam can be put, coal being regarded not only as a fuel but as the source of innumerable, and some perhaps unsuspected, materials of increasing importance in modern life. The ultimate aim of the research is a complete scientific knowledge of the chemical composition and mode of formation of coal.
Dr. Hickling desired to support all that had been said by the
Discussion on Coal. 517
preceding speaker regarding the supreme importance of the closest co-operation between chemical and microscopical investigators of coal-substance, and of both with the work of the field-geologist, if we are to ensure the most intelligent and profitable use of our coal resources. The great importance of the problems involved no one would question, and the experience he had had in their investigation had convinced him that only a considerable body of workers dealing in close co-operation with all branches of the subject could hope to attain in reasonable time to the endsdesired. Hestrongly hoped that this discussion might have such anissue. In one particular he desired to differ slightly from Dr. Stopes; while all agreed that every true coal was a mass of more or less decomposed vegetable material, he was inclined to suspect that, in general, it was the amount and character of the decomposition which determined the quality of the coal, rather than the nature of the original plants. Certainly it would be unwise to assume that any very intimate relationship must exist between the original composition of a given plant-structure, and the composition of the coal-substance into which that structure is now converted. Palzobotanists would remember that the most beautifully preserved plant-tissues consisted almost wholly of calcium carbonate or silica, and similarly in coal itself the original constituents of the cell-walls, etc., may be very extensively replaced by other materials, though the materials in this case are the decomposition products of the plants themselves. He regarded the co-operation of various classes of workers as especially necessary in discriminating the highly complex association of varied materials which entered into the composition of every coal-seam. The field-geologist readily recognized the sharply defined and distinguished ‘ bright’ and ‘dull’ bands or lenticles of the seam, while the microscopist was able to confirm the important differences between them. But the microscope enabled us to go much further, and to recognize that two samples of ‘bright’ coal, indistinguishable in the hand-specimen, are nevertheless widely different in minute constitution. The chemist, on the other hand, so far as any attempt at all had been made in the rational selection of material for analysis, had been in the habit of preparing a carefully mixed sample of all parts of the seam to be investigated. The analysis of such a sample, while possessing a certain commercial value, was clearly of the smallest possible value as a clue to the real constitution of any of the varied substances which are grouped together as coal. He was convinced that a scientific understanding of coals, the obvious pre-requisite of their best utilization, could only be attained by the investigation separately of the many distinct elements of seams which the eye and the microscope revealed. Professor Fearnsides expressed the hope that out of the present discussion would come a recognition by chemists that ultimate analyses of coals are required for purposes other than the mere determination of the equitable selling price of the coal by the truck. He dealt with the subject of coal as a rock genus, within which quite a number of essentially different species have already been distinguished by geologists and others, and asked that chemists should undertake to express these known differences in terms of the chemical constitution
518 Notices of Memoirs—Disecussion on Coal.
of the coals. He thought that all geologists would recognize the importance of the results which have been already obtained by the study of the behaviour of coals when extracted with various solvents. He had himself come up against some of the technical difficulties mentioned in the paper by Drs. Wheeler & Stopes, which invalidate the results which might be expected from the direct extraction of transparent micro-preparations of coal with pyridine or chloroform, but from his own experiments he was led to expect that the methods of the metallographer, applied to cleat surfaces or polished specimens of coal etched with these solvents, may provide the information which is immediately required. He wished to support Dr. Hickling’s contention that whenever a chemical analysis of a sound block of coal is undertaken, opportunity should be given for the paleobotanists to ascertain the microscopic structure of a corresponding portion of that same piece of coal. He expressed the opinion that great mutual advantage would accrue if the chemists would co-operate with field- geologists and mine workers in the choosing of the samples of coal which are worthy of analysis. He suggested in particular that one of the directions in which this co-operation between chemists and geologists was most to be desired was to secure a real knowledge of the lateral variations of composition within the individual lenticles of coal, which in sum constitute the wide-spreading beds of rock which are known as coal-seams.
Professor Boyd Dawkins emphasized the point raised by Dr. Hickling that the apparent identity in structure of certain parts of the coal with the cell-structure of the living plant does not necessarily prove that the original tissues of the plants have been preserved. It is a matter of common geological knowledge that very generally in the process of fossilization the original tissues, both of plants and animals, have been replaced atom by atom by carbonate of lime or silica, or even iron pyrites, without the details of structure having been destroyed. Sometimes, as in the case of the deposit of calcite in wooden troughs in coal-pits, the structure of the wood, including the growth-lines and medullary rays, is faithfully reproduced. In specimens in the Manchester Museum the calcite cast of the interior of sea-urchins, from the Coral Rag, has carried the pattern of. the test into the very centre, as the mineral slowly filtered through the wall. This point must be considered by the paleobotanists, who are doing their share of work in dealing with the history of coal. In his opinion the greater part, if not the whole, of the organic element in the coal had been subjected to mineral change.
Professor W. S. Boulton (who presided) expressed his gratification at the opportunity for an interchange of ideas among chemists and geologists upon a subject of vital importance to thenation. Already, much valuable research upon the nature and composition of coal had been done, both on the analytical and on the microscopical and palzo- botanical side. He felt sure that when the printed records of the discussion were published, they would serve to stimulate to fresh and more vigorous research, and more especially to co-ordinate and mutually assist the work of the chemist and geologist, and so enormously increase the value of our greatest industrial asset.
Notices of Memoirs—Ealing Scientific Society. 519
II.—Tue Eatine Screntirrc anp Microscoprcan Socrety.
The 39th Annual Report, issued October, 1916 (8vo, pp. xiv + 14), contains, in addition to the affairs of the Society, etc., abstracts of lectures given in the past year, viz.: (1) ‘‘ Coloration in Mollusca,’’ by B. B. Woodward, F.L.S., F.G.S., F.R.M.S.; (2) “‘ Meteorites and Shooting Stars,’? by Spencer L. Fletcher, F.R.A.S. (see below); (3) ‘‘ Colour Photography,’’ by Cyril M. Neaves; (4) High Explosives,’’ by George Senter, D.Sc., Ph.D., F.1.C.; (5) ‘‘Are the Planets Inhabited?’’ by H. Walter Maunder, F'.R.A.S.
Merzorites AnD SHoorrne Srars. By Spencer L. Fretcuer, F.R.A.S.
(J\HE ancients have left reports of stones falling from heaven which
were treated as being of supernatural origin, until scientific investigation of phenomena began. Until 150 years ago the scientist either doubted the actuality of such falls of stones, or explained them as caused by stones projected by terrestrial forces (such as whirlwinds or volcanic eruptions) or manufactured in the clouds from particles of dust. If a stone was found heated or partly melted the theory was that it had been struck by lightning. Such ideas were negatived by well-attested falls of meteorites, from that at Dijon in 1761, which could not be reconciled with such origins.
Mr. Fletcher showed a number of views of meteorites, photographed from actual meteorites in the Natural History Museum. He explained that they are divided into aerolites, which are of stone; siderolites, which are partly stone and partly metal; and siderites, which are wholly metal (usually iron mixed with nickel). In many cases their fall is accompanied by a flash of light and loud explosions. A single stone may be found or there may be a shower of stones (from bursting), as at Poltusk in 1868. A notable case was the great meteorite which in 1719 was visible from Aberdeen to Paris, and, passing over the length of England, appears to have fallen into the sea. In that instance, besides the bright light and explosions, the tremor of the air was noted by Halley. Another great siderolite fell at Estherville, Towa, in 1879, from a clear sky (showing that it had no connexion with clouds), and, bursting, scattered fragments over two miles, one weighing 431 pounds. The conclusion is that these lumps of stone and metal travel in outer space with great velocity, and burn away, wholly or partially, by friction, after entering our atmosphere.
They do not become visible until they reach our atmosphere, and have been observed at heights of 70 miles or less. It has been assumed that, at an earlier period of the earth’s history, it possessed much larger volcanoes than any now existing, which threw up stones with such force as to conquer gravitation, so that the stones, instead of falling back to the earth, remained travelling in orbits around the sun, re-crossing our own orbit at every revolution. To conquer the earth’s gravitation it would be necessary for the fragments to be projected with a velocity of at least seven miles per second. No volcano of the present day possesses sufficient power to do this, and there is no trace of the greater voleanoes which the theory supposes. This does not of itself, however, disprove the theory, as, since the earth’s primeval crust was produced, sedimentary strata amounting to many miles in thickness have been formed, and no
520 Notices of Memoirs—Ezeter’s Water Supply.
trace of the original crust remains. If the theory is applied to the moon, where there is less gravitation, and there undoubtedly were once immense active volcanoes, it accounts well for some of the slower moving meteorites, which may have been travelling round the sun in orbits which intersected our own, since the time when the moon’s volcanoes were active.
Their most probable origin is to be found in the primeval nebula, of which the comets are fragments. Comets travel in orbits round the sun, which are longer and narrower than the orbits of the planets. Passing too near a planet, a comet may become captured by its attraction, and have to revolve in a new orbit, which carries it around the sun, and then back to the place where the planet captured it. It thus becomes a short period comet.
When comets first become visible to us they are tailless, but as they approach the sun the tail appears and grows, and is usually repelled by the sun. The heat of the sun drives vapours out of the head of the comet (which consists of a cluster of meteors); the electrons thrown out by the sun condense these vapours into particles so small that they can be repelled by the sun’s light against gravitation, thus forming the tail. The tenuous character of the-tail is clear from the fact that it does not obscure the stars from our vision.
To sum up the history of these bodies, Mr. Fletcher went back to the nebula, from which all stars are formed. It condenses into a system like our Solar System, but some fragments or wisps are left out, which form the heads of comets and travel round the central sun in long orbits. They are caught by planets and reduced to smaller orbits. The emission of the tail gradually wears them out till they become tailless, and are reduced to streams of meteors. These get in time strewn round their orbits. Then the question arises, are meteorites and shooting stars the same? In general it would seem so, but in that case the meteorites which reach the earth in tangible form must be the very largest shooting stars, as the usual shower of them only produces the finest dust.
IIJ.—Hisrorican Manuscripts Commission: THe Earty WATER SuppLy oF EXETER.
ik the Report on the Records of the City of Exeter, just issued by the Historical Manuscripts Commission (characterized by the halfpenny Press as ‘‘ waste of paper’’), will be found the following interesting documents relating to the water supply of Exeter City.
‘©1260. The Prior and Conyent of St.’ Nicholas grant leave to Martin Durling and his heirs to draw water ‘ab aqueducto que est in cemeterio nostro ce Occidentali parte ecclesia nostre per gardinum nostrum quod est in occi- dentali parte que ducit a magno vico usque ad Fratres Minores’.”’
“1299. Agreement on the part of the Mayor and Commonalty of Exeter by consent of Edmund, Earl of Cornwall, with Henry de Bolleg’, Archdeacon of Totnes, concerning the building of a tower next the said Archdeacon’s house—
‘ per quam communis aqua civitatis ingreditur.’ ’’
‘©1346. Settlement of a dispute between the Prior of St. Nicholas on the one side and the Dean and Chapter of the Cathedral and the Mayor, etc., on the other, in regard to the making and repairing of the common water ‘conduit’, the water of which rises “without the East Gate in St. Sidwell’s parish.”’
ee
Reviews—Geology and the Panama Canal. 521
‘1347. King Edward III grants to the Warden and Convent of the Grey Friars of Exeter ‘quod ipsi duos modicos [sic] atque ortus se jungentes in pro- funditate fossati civitatis Exon inter orientalem et australem portas ejusdem civitatis profundius fodere et muro lapideo basso includere et aquam de ortibus illis sive fonte inde facto exinde per fistulam subterraneam in fossato predicto et ultra stratam regiam usque ad domum sive habitacionem fratrum pre- dictorum, qua in loco sicco situatur et ad quam aque cursus non habitur, ponendam ducere ac caput fontis predicti dictamque fistulam quotiens reparacione et emandacione indigent reparare et emendare ac de novo construere et facere prout magis expedire viderint’, etc.’’
‘©1444, The chamber obtain licence to dig for water in St. Sidwell’s Fee and to carry away the water in leaden pipes to the new conduit.”’
1534. ‘Mdm. that John Newtun and John Geboons beganne to make the erete condet of Exsetur the viij day of Novembre, and here folowyth the costes and charges.’ ‘ Thys ys the hole boke, the sum thereof trewly caste as y can do—xxyiijlt. xjs. viijd.’ ”’
** 1600 and 1649. Contracts made to lay new leaden pipes to the conduits and cisterns of the city.”’
“1694. Contract concerning the waterworks and the supplying of the city with water. And in 1695 the Mayor, etc., make a grant of the waterworks of the city and several parcels of land for a term of 200 years.”’
The last document brings the matter almost to our own days.
RAVIEwWwS.
i Sere 1.—Gronocy AND THE Panama CANAL.
(TVHE United States Department of the Interior (Bureau of Mines)
has issued a Bulletin (No. 86) by Donald F. Macdonald on ‘Some Engineering Problems of the Panama Canal in their relation to Geology and Topography”. ‘his extremely interesting publi- cation (price 45 cents) deals with topographic types, climate, streams, valleys, coastal conditions, and their several relations to the works. It discusses the general geology and its connexion with the engineering problems as found in the sedimentary and the igneous masses cut through. Then with the structural geology, folding, faulting, shearing, fissuring, jointing, and in- trusions; values of the various rock material for constructive work ; stability of foundation rocks and conditions affecting the same; slides, their causes and remedies, with full details of the canal slides and illustrative slides from other areas and their cure; local heating of rock masses by chemical decomposition on weathering, by drilling or blasting ; danger from earthquakes or earth-movement, ete. All which matter can be applied to any constructive works according to varying local conditions, and therefore of considerable value in handy octavo form. The pamphlet closes with a tabulation showing the cost per cubic yard of dry excavation, crushed stone, coarse rock, sand, masonry, etc., and provides bibliographies of ‘slides’ and methods of mining.—C. D. 8.
IJ.—Tuicknessres oF STRATA OF THE CounTIEs or ENneLanD AND Wats. Memoirs of the Geological Survey. pp. vi+ 172. 1916.
NDER this title the Geological Survey have issued a summary of
the chief facts regarding the thicknesses of the newer strata
of England and Wales. The authors wisely limit themselves to
522 Reviews—Geits. Gubib, an old Volcano.
strata newer than the Carboniferous; since, as is set forth in the preface, measured thicknesses of rocks older than this period are of little or no value; while as for the Carboniferous system itself, © records are so numerous that there is little need to repeat them. The country is divided into counties, which are described either singly, or two or three together, where geographical or geological conditions make this necessary. ach area by itself forms the subject of a chapter, beginning with a map showing, as far as possible, all the places mentioned in the text. A general description of the rocks follows, beginning with the newest and going down to the oldest, in which the most important variations in thickness of each formation are discussed. Finally, a tabulated list of the records of the principal deep borings is added at the end of the chapter. The book affords an admirable and simple method of obtaining much information which could only be obtained hitherto by prolonged search through libraries.—W. H. W.
III.—Gaurrst Gupin: an Oxp Vorcano. By A. W. Rogers. Trans- actions of the Royal Society of South Africa, vol. v, pt. iii, December, 1915.
EITSI Gubib is a ring-shaped mountain, rising 5,200 feet above sea-level, and 1,800 feet above the plateau north of Keetmans-
hoop in South-West Africa. The ring is from one mile to a mile and a quarter in diameter, and has a depression in the centre 1,500 feet below the highest point of the ring, which is drained by a stream flowing through a gap in its south-east side. The mountain itself is composed of fine-grained clastic rocks dipping steeply inwards. The junction with the Fish River Sandstones is vertical, and can be seen in the valley of the stream; in the same place it can be seen that the sandstones also dip inwards at the junction. ‘The rocks themselves consist of breccias and tuffs; the breccias are formed of fine-grained sedimentary rocks, with some fragments related to the quartz gabbros, in a cement of quartz and dusty material. Fragments of orthoclase, plagioclase, and augite are found in them. The most notable features are the entire absence of true volcanic rocks and of large blocks, there being none above oneinchin diameter. ‘he silica cement seems to be harder and better developed round the outside of the mountain, and it is to this fact that it owes its ring-shape. This disposition of the cement is almost certainly due to the rising of waters charged with silica round the margin of the vent. No trace of the fragmental material which was thrown out on to the surrounding country now remains, and it is obvious that the original cone and surface have been worn away, leaving the hardened plug standing above the present plateau. The depression in the centre is therefore not acrater, though it occupies the same relative position. Dr. Rogers suggests two possible origins for the mountain; these are, first, that it was an ordinary explosive crater, and second, that the clastic rocks have been let down by a circular fault. Of these the first is more probable, as there is little brecciation along the line of junction; and it is also borne out by the existence of sattelite pipes with igneous
Reviews—Zircon, Monazite, etc. 523
material in the neighbourhood. The age of the mountain is quite uncertain ; it may be post-Karroo, as a fragment of rock, probably of Karroo age, was found in the vent, but this is by no means proved.—W. H. W.
IV.—Zrrcon, Monaztrz, and orHEeR MINERALS USED IN THE PRo- DUCTION oF CHEMICAL CoMPOUNDS EMPLOYED IN THE MANUFACTURE oF Ligeutine Apparatus. Bull. No. 25, North Carolina Geological Survey. 1916.
TP\HIS publication with a clumsy title contains a very interesting
account of the occurrence and exploitation of the large number of rare-earth minerals that are now used in the manufacture of incandescent gas-mantles and filaments for electric lamps. The minerals now used on a large scale for these purposes are monazite, zircon, gadolinite, columbite, tantalite, and wolframite. Other minerals capable of being used for the same purposes if found in sufficient quantity are also dealt with. As is well known, many of them are found in considerable quantity in North Carolina, especially monazite and zircon. The processes employed in mining and manufacture are also described in an attractive manner.—R. H. R.
V.—Grotocy oF THE CranBrook Map-area, British Cotumpia. By S. J. Scnorrerp. Canada, Dept. of Mines, Geological Survey Mem. 76. pp. 245. Ottawa, 1915.
{J\HE area described in this memoir consists mainly of the central _ portion of the Purcell. Range, an area that once formed the western flank of the ancient Rocky Mountain geosyncline. A detailed account of the Purcell Series (of Beltian age) and of the well-known Purcell and Moyie sills is given. On the east the Purcell sediments continue underneath an unconformable blanket of Palaeozoic forma- tions, while to the west there still remain patches of pre-Beltian schists that seem to be relics of the parent land from which the Purcell Series was derived. The Purcell sills consist of hornblende gabbro accompanied by irregular masses of hornblende granite, and with the latter copper deposits of some importance are associated. However, the area owes its economic prosperity more particularly to the presence of valuable silver-lead deposits associated genetically with small stocks of granite that for the present are thought to be of Jurassic age. The memoir is copiously illustrated with thirty-three plates and is accompanied by a coloured geological map.—A. H.
VI.—THE Grorocy or Paranyspa anp Rio Grande po Norte, Brazit. By R. H. Soper. Proc. Am. Phil. Soc., vol. li, pp. 1-20, 1916.
ITH the exception of a narrow belt along the coast and a few isolated patches of the interior, the whole of the two states is
made up of the crystalline rocks known broadly as the Brazilian complex. This consists of gneisses and schists thickly threaded with quartz veins and pegmatites, and intruded upon by numerous bosses of granite which form the axes of the principal serras. Along the
524 Reports & Proceedings—Geological Society of Glasgow.
coastal belt the rocks are sedimentary and range in age from Cretaceous to Recent. The author divides them into three groups: (1) sandstones with fossils; (2) limestones belonging to the late Cretaceous and early Tertiary; and (3) sands and clays (probably of late Tertiary age) surmounted in places by recent sand dunes and other deposits. The topography of the country seems to approximate to the ‘inselberg’ type of landscape, for Mr. Soper describes it as ‘‘characterized by great undulating plains, abrupt mountains, rocky, steep-sided hills, and peaked serrotes””.—A. H.
VIJ.—Nepuerine Syenires or Hatrsurton Country, Onrario. By W.G. Foyr. Am. Journ. Sci., vol. xl, pp. 413-86, October, 1915.
f{\HE author describes two differentiated laccoliths of nepheline syenite that lie in a syncline of limestone between large areas of Laurentian gneiss. He then discusses the origin of the alkaline intrusions, and states his agreement with Professor Smyth’s opinion that nepheline and sodalite rocks are results of the pneumatolytic phase of igneous activity in certain circumstances. In this instance Mr. Foye suggests that the controlling circumstances consisted in the desilication of granite magma during its lit-par-lit injection into the Grenville limestones. ‘‘Soda solutions were given off by the granite magma because lime was capable of replacing soda at high temperatures”’ (p. 434). From granite and limestone as the parent materials, amphibolite and nepheline syenite were, it is believed, thus derived, and the close field associations of these four types of rock provides the theory with an assemblage of facts that ought on further elucidation to lead to its complete demonstration.— A. H.
REPORTS AND PROCHEHDINGS.-
Grotogicat Socinry or Graseow.
At a meeting of the Society on October 12, Mr. G. W. Tyrrell exhibited, on behalf of Mr. B. K. N. Wyllie, a number of Stone Age artifacts from Northern Ashanti. These are of three types: (1) rough chips and flakes of quartz; (2) chisel- or celt-shaped polished stones; (3) artifacts with a herring-bone or cross pattern. The first two types are common throughout the Gold Coast Colony, but the third is rare, the specimens exhibited being found at Temma, 100 miles north of Coomassie, in a remarkable natural stronghold. The latter consisted of a rectangular block of current-bedded sand- stone, 200 to 300 yards long by 100 yards broad, and nearly 200 feet high, standing with sheer walls on the low slope at the side of a wide valley. The patterned objects and the celts were found on the floor of a small cirque inside this, which may have been adopted as a fortress or a fetish monastery by an earlier race of inhabitants; the local Ashantis display utter ignorance of the originators of these things, and their fetish methods are totally different. A piece of iron slag was also found inside the cirque.
Obituary—C. T. Clough. 525
Dr. C. H. Desch read a paper, illustrated by lantern slides and specimens, on ‘‘ The Origin of Agates’”’. The most puzzling question in regard to agates was the parallel banding of the chalcedony of which they were chiefly composed. This had usually been regarded as representing successive flows of liquid containing gelatinous silica, which was deposited in thin layers on the walls of the cavity in which the agate was formed. Certain features common in agates were regarded as ‘‘tubes of entry” or ‘‘tubes of escape’’. In 1867 Ruskin had brought forward evidence to show that the banding was due rather to segregation in the solid state, but no theory as to the mechanism of the process could then be given. The work of Liesegang on rhythmical precipitation in gelatinous masses had led to the production of objects in which all the characteristic features of agates, including the ‘‘ tubes of escape’’, were exactly imitated by processes of simple diffusion. It was not even necessary to assume precipitation. Slides were shown to prove that rhythmical crystal- lization, giving rise to a banded structure, could be observed even in pure substances. It was sufficient to assume a process of rhythmical erystallization in a mass of gelatinous silica to account for the banding and other characteristic features of agates.
OBITUARY.
Gane CLOUGH; M.A., LL.D., F.G.S., F.R.S.E., of Geological Survey of Great Britain.
BoRN DECEMBER 23, 1852. DIED AUGUST 27, 1916. N accident on the railway near Bo'ness has cut short the life of one of the most widely known and deeply respected of British geologists. Dr. Clough in the course of field-work in that district had occasion to cross the railway. Some mineral wagons were being _ shunted at the time and he tried to passin front of them, but was run over. Immediate attention was given to him, first by the railway staff, and thereafter by the surgeons of Edinburgh Infirmary, to which he was sent by special train, but his injuries were very serious, involying double amputation, and after lingering for three days he died on Sunday, August 27, 1916. He was buried in Lasswade Churchyard on Wednesday, August 30.
Dr. Clough was 63 years of age. He joined the Geological Survey in March, 1875, at the age of 22, and after forty-one years was on the eve of retiring, but consented to remain on the staff to assist in meeting the pressure of work entailed by the absence on active service of most of the junior members of the Survey.
He was educated at Rugby, and at St. John’s College, Cambridge, which he entered in October, 1871. He was awarded an exhibition in Natural Science from 1872 to 1874. In 1873 he obtained a first _ class in the May examination. In 1874 he received a first class in the Natural Science Tripos, being bracketed second with Herbert Carpenter, J. N. Langley, R. D. Roberts, and C. E. Shelly. He was elected a scholar in 1874-5, and took his B.A. in 1875 and his M.A. in 1878.
526 Obituary—C. T. Clough.
His first work on the Survey was done under the late H. H. Howell in the North of England. Teesdale, a district for which he preserved a lifelong affection, was the scene of his earliest field-work ; and his first paper, printed in the Quarterly Journal of the Geological Society in 1876 (vol. xxxil), was on ‘‘ The Section at the High Force, Tees- dale”. He continued in Northumberland and Durham for eight years, and the results of his work appeared in several Surve memoirs, including Otterburn and Elsdon (Sheet 108 8.E.) and Zhe English Side of the Cheviot Hills (Sheet 108 N.E.).
In 1884 the one-inch map of England and Wales was completed, and Clough, along with Gunn, Barrow, and Hugh Miller, was trans- ferred to Scotland. The survey of the North-West Highlands was then beginning, and Clough took part in it, but in the autumn and spring seasons he was engaged in surveying the Cowal district of Argyllshire. In Sutherlandshire he mapped a large district north of Loch Glencoul to Loch Inchard, and subsequently he executed the survey of an extensive area around Loch Maree. His description of that ground is contained in the Survey memoir on the North-West Highlands. When this was completed he worked in Glenelg, the north-east part of Skye, and Soay. About 1900 he was transferred to Strathcarron, Eastern Ross-shire. In 1902, on the death of W. Gunn, Clough became a District Geologist. He continued for a time in Ross-shire, and subsequently took charge of the work in northern Argyllshire and in Mull. In the spring and autumn seasons he was also employed on the revision of the coal-fields which was started in 1900. His first work of this description was in Haddingtonshire and the Lothians coal-field, and when that was completed he was trans- ferred to Bo’ness. Subsequently he had charge of the revision of the Lanarkshire coal-field in the district south-east of Glasgow (Holytown, Motherwell, Airdrie), and finally he superintended the work in the North Ayrshire coal-field.
As time went on he exhibited a certain reluctance to publishing geological papers in the transactions of societies and in journals, and most of the results of his field-work appeared in Survey memoirs and maps. Of these perhaps the best known are the Geology of Cowal (1897), Geology of the Neighbourhood of Edinburgh (1910), Geology of the Glasgow District (1911), Geology of Ben Wyvis (1912), and the Geology of Glenelg (1910). At the time of his death he had two important memoirs on hand, viz. The EHconomic Geology of the Central Coal-field of Scotland and the Geology of Mull. Dr. Clough had contributed to thirteen Scottish and five English memoirs of the Geological Survey.
In field-work and the preparation of maps Dr. Clough found his principal interest. Office work and the writing of memoirs and scientific papers were more or less irksome to him. He combined to an extraordinary degree powers of minute observation, great diligence, and enthusiasm. His working day was always a very long one, and no difficulties arising from the complexity of the structural features of the ground assigned to him ever depressed him. In fact, he revelled in the mapping of intricate geology. Some of his field maps of the. North-West Highlands, of Mull, and of Central Ayrshire may be
Obituary—C. T. Clough. 527
cited as examples of detailed mapping on the six-inch scale which, for thoroughness, have never been surpassed. He wasa very judicious and impartial observer, and extremely cautious in drawing inferences. These qualities were especially valuable in mapping the Scottish coal-fields, where faulting and igneous intrusions play an important part. Mining engineers freely recognized Dr. Clough’s pre-eminence in this class of work and placed great reliance on his opinion. The excellent training which he received from H. H. Howell no doubt laid the foundation of his eminence in field geology.
Inthe much debated questions of Highland geology and metamorphism Dr. Clough was intensely interested, and keenly alive to the importance of new discoveries. Yet he avoided speculation and declined to formulate general hypotheses till he felt sure the evidence was sufficient. Once convinced, however, he took up a well-defined position and was able to maintain it against all critics. His contribu- tions to the memoir on Ben Wyvis shows a broad grasp of the problems involved. In later years he was a strong supporter of the interpretation of the structure of the Fort William country which was advanced by Bailey and Maufe. The important paper on the Cauldron Subsidence of Glencoe, which he wrote along with the two above-named geologists, had wide bearings on the tectonics of the Highlands. The still more difficult problems of the Tertiary Volcanic Rocks of Mull during the last years of his life deeply absorbed his attention.
He had a strong personality, which has left its stamp both on his work and on the men whom he trained in field geology, many of whom have attained distinction in scientific work. His watchwords were thoroughness and veracity, even in the minutest, apparently insignificant details. His habits were of extreme simplicity, and he was perfectly content with the rough food and simple life of a High- land shepherd’s cottage. One of the most unassuming of men, he was never known to utter a harsh criticism, and he treated the opinions of even the youngest geologist with sincere respect. His gentleness, kindness of heart, and helpfulness earned him the affection of all with whom he came in contact. Questions of social reform attracted him strongly, though he paid little attention to politics as a whole.
Dr. Clough was a Fellow of the Royal Society of Edinburgh, and of the Geological Society of London, which, in 1906, awarded him the Murchison Medal. In July of the present year the University of St. Andrews conferred on him the honorary degree of LL.D. He was President of the Geological Society of Edinburgh from 1908 to 1910. He leaves a widow, two daughters, and a son, who is now in Canada and is serving with the R.A.M.C.
MISCHLUAN HOUS.
Human SkeLeton in GrAcz4t Deposits, Ieswice.!
We have received the following letter published in the Zvening Star and Hast Anglian Daily Times (dated October 14, 1916) :—
1 See GEOL. MAG., 1912, pp. 165, 187, 239, 287.
528 Miscellaneous—The Ipswich Human Skeleton.
‘“Mr. J. Reid Moir writes:—It will no doubt be remembered that at the time of the discovery in 1911 of a human skeleton in a sand pit in the occupation of Messrs. A. Bolton and Co., Ltd. (late Bolton and Laughlin) of Henley Road, Ipswich, it was held by some geologists and by myself that the remains occurred beneath an undisturbed stratum of weathered chalky boulder clay. Since this discovery I have been enabled to investigate extensively the small valley adjoining the sand pit in which the human skeleton was found, and to conduct excavations in the immediate vicinity of the spot where the bones occurred.
‘These investigations have shown that at about the level at which the skeleton rested the scanty remains of a ‘floor’ are present, and that the few associated flint implements appear to be the same as others found on an old occupation-level in the adjacent valley. This occupation-level is in all probability referable to the early Aurignac period, and it appears that the person whose remains were discovered was buried in this old land surface. The material which has since covered the ancient ‘floor’ may be regarded asa sludge, formed largely of re-made boulder clay, and that its deposition was probably associated with a period of low temperature occurring in post-chalky boulder clay times.
‘Tt appears, then, that the human skeleton found is referable to a late Paleolithic epoch, and cannot claim a pre-chalky boulder clay antiquity. I wish to take this opportunity to state that those who opposed my contention as to the great age of these remains were in the right, while the views held by me regarding them have been shown to be erroneous.”
Tue Swivey Lecrures on Gerotogy, 1916.—The Trustees of the British Museum (Natural History) announce that a course of twelve lectures on the Mineral Resources of Europe (illustrated by lantern slides) will this year be delivered by Dr. John S. Flett, F.R.S., at the Royal Society of Arts, 18 and 19 John Street, Adelphi, W.C. (by permission of the Council of the Society). The lectures will be given on Tuesdays, Thursdays, and Fridays, at 5 p.m., beginning Tuesday, November 14, and ending Friday, December 8. Admission free.
ERRATA AND ADDENDUM to Mr. Leonard Hawkes’s abstract of paper read at British Association (see GEOL. Mac. for October): p. 468, 1. 10, for Borganfjord read Borgarfjord; 1. 11, for Bernfjord read Berufjord; p. 469, 1. 8, for ice-scratched boulder read ice-scratched liparite boulder.
ERRATA in Mr. P. G. H. Boswell’s abstract, October, pp. 466-7: §1,1. 5, for rise above 0°5 per cent read rise above 0°02 per cent, and (two lines lower) for 0°02 per cent read 0°5 per cent. § 3: the opening paragraph should read : ‘*as simple as possible ; the sand ought to contain only quartz.’’ In the next paragraph the fourth sentence should read: ‘‘ The important supplies of glass- sands occurring in Western Europe are all associated with planty material, Lippe sand occurring with rafts of braunkohle.’’ For the locality Hohenboka read Hohenbocka, and for Berrythorpe read Burythorpe.
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Ta Be BS Sh SS fig 2 he
I. ORIGINAL ARTICLES. Page NOTICES OF MEMOIRS (cont.). Page Address to Geographical Section, British Association, 1916, on
Eocene Corals from Central New Guinea. By J. W. GREGORY and
_JHAN B. TRENCH. (Plates XXI- Mapping the Karth. By Edward cua a Text- ame) Os — ee ee F.R.G.S. a clude “i Fg eee vee bia tees Ill. REVIEWS. She ee a Age, and Glacier Professor Sollas: Serial Sections of ee aenss By Shea eee the Skull of Ichthyosaurus ... 571 ES ee Types of Prismatic Structure ws O12 ee at ieure. eae SANE eS W. H. Collins: Killarney Granite 572 Pit and Mound etenne: de- G. M. Davies: Rocks and Minerals, E veloped during Sedimentation. By Croydon ee Oe Ete hig een eee
EB. M. KinpDue. (Plate XIII.)... 542 | Miller and Knight: Metals in Pre-
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Il. Novices OF MEMOIRS. Geological Society of London... 574 | Address to Geological Section, Mineralogical Society ... ... ... 575 \ British Association, 1916, on our V. OBITUARY. Coalfields, ete. By Professor Bedford McNeill, A.R.S.M., Memb.
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Photos by S. Fingland. EOCENE CRETACEOUS CORALS, NEW GUINEA. Actinacis, Kobya.
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NEW SERIES. DECADE VI. VOL. III. No. XII.—DECEMBER, 1916.
ORIGINAL ARTICLES - —_—_@—_
T.—Eocenrt Corats From THE Fry River, Centra New Gorvea. By J. W. GREGORY and JEAN B. TRENCH, University of Glasgow. © (PLATES XXI-XXII.) (Concluded from the November Number, p. 488.)
Actinacts, D’Orbigny, 1849. Actinacis maitlandi,’ n.sp. (Pl. XXI, Figs. 2, 3.)
Diagnosis.—Corallum massive and probably nodular. Corallites polygonal, often pentagonal, and, where the walls are not well defined, appear circular. Calices from 2 to 3mm. in diameter; the width of coenenchyma separating them varies from ‘5 to2mm. Septa twenty-four in number, subequal; the trabecule are distinct in some and in others fused together. Pali rounded; they occur in three crowns, the primary pali being larger than the others. They are sometimes quite separate from the septa, and sometimes completely fused with the septal ends. Together with the columella they occupy a space equal to one-third of the diameter of the calyx. Columella fairly large, though somewhat irregularly developed. Occasionally it is so small as to appear papilliform, but it is generally clearly fascicular.
Dimensions.—Diameter of corallites, 2-6-3mm.; distance of calicinal centres, 3-5 mm.
Figures.—P\. XX1, Fig. 2a, thin transverse section; x 6 diam. Fig. 20, polished surface of same; x 6. Fig. 3, thin transverse section of another specimen; X 6 dia.
Affinities. —This species is represented in the collection by three specimens (Nos. 20, 26, 37). It resembles the type species A. martiniana, Orb. (1849, p-11), in the number and arrangement of septa, but the calices are nearly twice as large and the coonenchyma is much more sparse. It approaches more nearly to the A. remesz, Felix (1903, pp. 567-7), but the calices are greater than those of the latter and the ccenenchyma is also considerably less. Trauth (1911, p. 79) has described a new species, A. retifera, which has round or sub-polygonal calices, some of which equal A. maitlandi in size. The ccenenchyma, however, differs both in amount and character, and the columella is rudimentary. ‘These species are all Cretaceous. Of the Kainozoic species, A. noetlingi, Dalton (1908, p. 622, pl. liv, fig. 1), from the Miocene of Burmah, resembles. our
1 After Mr. A. Gibb Maitland, one of the geological pioneers in British New Guinea. DECADE VI.—VOL. II.—NO. XI. 34
530 J. W. Gregory & Jean B. Trench—
species in calicular characters; but its calices are much more widely separated, the centres being from 10 to 11 mm. apart, and the corallum is dendroid.
An Eocene species, 4. digitata, from Borneo, has been described by Fritsch (1875, p. 129, pl. xvii, fig. 7); it differs very considerably from A. maitlandi; its calices are smaller, the pali are more prominent and regularly arranged around a small columella, which on the surface appears styliform ; the corallum, moreover, is dendroid.
Actinacis sumatraensis (Tornquist), 1901. (Pl. XXI, Fig. 1s)
Neostroma sumatraensis, Tornquist, 1901: ‘‘ Ueber mesozoische Stromato- poriden,’’ Sitz. k. preuss. Akad. Wiss., 1901, pp. 1117-20, figs. 1-5. Actinacis sumatrensis, Gerth, 1909: ‘*‘Echte und falsche Hydrozoen aus niederlandisch-Indien,’’ Sitz. Niederrhein. Ges. Natur. u. Heilkunde zu
Bonn, Abt. A, 1909, pp. 21-3.
This species is represented by one specimen, No. 14. It agrees closely with the Sumatran Cretaceous species A. sumatraensis (Tornquist), though the septa in the latter are thinner, longer, and more irregular, while the calices are slightly larger and closer together. In A. cymatuclysta (Felix, 1906, p. 43, pl. ili, figs. 4, 4a) the calices are almost of the same size and shape, but the primary septa at least reach the columella, which is feebly developed, though the pali are distinct.
Porirrs, Lamarck, 1816. Porites deshayesana, Mich. (Pl. XXII, Figs. 2a, b.) Porites deshayesana, Mich., 1844, p. 164, pl. xlv, fig. 4.
The collection includes one specimen (No. 28) of a Porites which agrees in early all respects with the above species. If, however, Bernard (1906, p. 109) were right that the calices of P. deshayesana are less than 1mm. in diameter, it would differ in that important respect. Bernard states that his estimate of the dimensions is based on Michelin’s original figure, in which, according to our measure- ments, the corallites are shown as at least 1°5 mm. in diameter. They thus agree with those of the New Guinea Porites. The character of the septa are shown by the accompanying drawings of three corallites from a section (see Text-figure).
Sse ve} & ee 638
Porites deshayesana, Mich., var. inequisepta, n. var. Transverse sections of three corallites. Upper Fly River, New Guinea.
The septa appear to be thicker and more unequal in size than in the typical form of the species. Accordingly we feel bound on that character to separate this coral as a distinct variety and name it var. dnequisepta.
Amongst other Eocene species this Porites agrees by its ill-defined columell: and indistinct wall with Porites heberti, Ed. & H., sp. (1850,
Tocene Corals, Central New Guinea. 531
p- 89; Hist. Nat. Cor., vol. 111, p. 187), but in that species the septa are more equal and the corallites are 3 mm. in diameter.
P. belli, Greg. (1900, p. 223), from the Miocene or later rocks of Christmas Island, is an allied species, but has better developed walls.
Monripora, Quoy & Gaimard, 1833. Montipora antiqua, u.sp. (Pl. XXII, Figs. 1a, b.)
Diagnosis. —Corallum massive. Corallites long and thin. Calices circular and shallow; their diameter is about half the width of the distance between the calicinal centres. The calices are surrounded by a zone of porous tissue. The corallites are separated by short straight lines of more compact ccenenchyma, which gives the corallum in section the appearance of being composed of prismatic corallites. Septa twelve in number; they consist only of spines. Columella conspicuous. Pali absent.
Figures.—Pl. XXII, Fig. la, photograph of a polished transverse section (No. 36); x 3diam. Fig. 10, polished vertical section of the same specimen ; x 3 diam.
A finities.—This interesting coral has the structure well preserved on the surface which was first polished. A microscopic section was cut from the lower part, but the material there has been altered, and the intimate structure is less satisfactorily shown. The coral, owing to its spiny septa and massive porous ccenenchyma, belongs to the Montiporide.
Among the living species of Montipora this species is nearest to those which, like Jf. "hirsuta, Bernard (1897, p. 164, pl. xxxiv, fig. 16), have a columella and the calices separated by a perforate wall that rises, as in J. calcarea (Bernard, 1897, p. 59, pl. xxxil, fig. 13), to a distinct ridge. If these two characteristics were always associated, as in I. antiqua, species in which they are present should be separated as a distinct genus or subgenus. ‘The recent species that have a columella occur in each of Bernard’s five sections of the genus; for among the glabrous group it occurs in JL exserta, Quelch ; in the glabro-foveolate in Jf. spatula, Bern. ; in the foveolate in IW. calearea, Bern. (though no columella is shown in Bernard’s figure of that species, 1897, pl. xxxii, fig. 13); in the papillate in JL verrucosa, Lam., MM. venosa, Ehr. (not shown in Bernard’s figure, pl. xxxu, fig. 16), and M. spumosa, Lam.; and in the tuberculate in IL friatilis, Bern., J. ellisi, Bern., I. efflorescens, Bern., MW hirsuta, Bern., and I. incognita, Bern. Asthese five groups are based on so variable a feature as surface ornamentation they appear artificial, and the presence of a columella and of the immature wall in the coenenchyma are probably more constant and reliable characteristics. Milne Edwards and Haime in their diagnosis of Montipora say that it has neither columella nor pali.! But Bernard has shown that a columella is present in some recent Montipora, such as MW. ellisi and I. floreseens. Though it is inconsistent with the practice throughout the rest of the Madreporaria to leave in one genus species with and species without
1 Duncan, by an obvious slip, wrote ‘‘ with columella and pali’’, whereas it should probably have been “‘ without columella and pali’’.
532 J. W. Gregory & Jean B. Trench—
a columella, as that course has been adopted for the recent Montipore it seems advisable to follow it.
The genus Montipora is confined in range to the western Pacific, Indian Ocean, and Red Sea. A fossil specimen has been recorded from the raised beaches of the Gulf of Suez (Gregory, 1906, p. 117), and a living species from the Pliocene of Borneo (Felix, 1918, p. 326); but otherwise it appears to be unknown fossil. The occurrence of this Eocene Montiporid is of interest, as it throws light on the disputed question as to the affinities of the family. According to Dana (1848, p. 490), Montipora (which he calls MManopora) is a degenerate MMadrepora. This view has also been accepted by Bernard (1897, vol. iii, p. 12). Milne Edwards and Haime, on the other hand, regarded Montipora as a Poritoid with an abundant coenenchyma; and this view has been adopted by Duncan. ‘The essential difference between the Poritide and the Madreporide appears to be the character of the septa. In Madrepora they are lamellar ; in the Poritide they are reduced to irregular trabecule. In this characteristic Jfontipora is more similar to Porites than to Madrepora. Bernard argues that the characters which give a trabecular character to the coenenchyma of JD/ontipora are shown by his investigations to be secondary structures. It might therefore be inferred that the trabecular nature of the septa is also secondary. But in the Eocene Montipora the septa are spines and not lamelle ; this characteristic was fully developed in the earliest known species ; and that fact supports the view that the Montiporide are more nearly related to the Poritide than to the Madreporide,
Tue Ace anp RELATIONS oF THE FAUNA.
The affinities of this fauna as a whole, with the exception of the one Cretaceous species, are Eocene, but geographically it is too isolated to be satisfactorily referred to the precise subdivision of that system. Mr. R. B. Newton, who is kindly describing the associated foraminiferal limestones, tells us that their age is probably Lutetian (Middle Eocene); and the coral fauna is consistent with that opinion.
It has been long known that New Guinea includes a rich and varied series of Kainozoic deposits, which range from the Eocene to the Pleistocene. They include thick beds of foraminiferal limestone which in Dutch New Guinea form precipices (Rawling, 1911, p. 244, and Wollaston, 1914, pp. 257, 265) that have been described as the loftiest in the world. ‘The rocks have a general trend east and west, and they are represented by similar rocks on the western islands of Malaysia. .
The best known of the Kainozoic deposits of New Guinea are the foraminiferal beds, which include Eocene limestones with Wummulites and Alveolina, Miocene orbitoidal limestone, and in the Upper Pliocene or Pleistocene widespread foraminiferal oozes or marls (e.g. Schubert, 1910, p. 326), which indicate an extensive subsidence in very recent geological times. A valuable summary of the informa- tion regarding these foraminiferal limestones and full references to
Eocene Corals, Central New Guinea. 533
the literature on them has been recently given in the memoir by Mr. R. B. Newton (1916).
In British New Guinea the first known Kainozoic beds were the Plocene and Pleistocene. A review of the earlier literature was given by Mr. Robert Etheridge, fil. (in Thomson, 1892, pp. 208-15, and in Jack & Etheridge, 1892, pp. 696-7). At that date the beds best known were those in the neighbourhood of Yule Island and the adjacent parts of the coasts of south-eastern New Guinea; and they are Pliocene and Pleistocene in age. Mr. Gibb Maitland refers (18938, p. 62) in his valuable memoir on the Geology of British New Guinea to the occurrence of the raised coral reefs ranging from sea- level to the height of 2,000 feet; and he remarks that there is no reliable evidence as to their geological age. Subsequently Eocene beds were recorded from Dutch New Guinea, as in the Wilhelmina Mountains (Martin, 1911) and at Triton Bay; and also in German New Guinea, as in the Torricelli Mountains and Humboldt Bay (Rutten, in Wichmann, 1914, pp. 42-3), in Celebes (Biicking, 1902), in Sumatra (Volz, 1904, p. 89), and in Java (Martin, 1900, 1915, ete.). The Kocene foraminiferal limestones no doubt represent the great Nummulitic limestone of the Mediterranean and Southern Asia, for some of them are referred to the Middle Eocene. Beneath this marine series there are in many places continental deposits sometimes containing coal (as in Java, Martin, 1900, p. 243) and sometimes yielding oil. Owing to this association of land and marine deposits it is natural to find that shallow-water beds with reef-building corals frequently occur in the Eocene beds. Thus Biicking (1904, pp. 177, 149) quotes Koperberg as authority for the existence of coral limestones in Celebes up to 1,000 metres above the sea, and Retgers for the occurrence of corals with Mummulites at Malawa in Celebes. Comparatively little has, however, been published on the Eocene corals of this Archipelago. The most important communication is that by Fritsch (1875) on the Eocene corals of Borneo. Martin (1881, pp. 73, 82-3) quotes Pleistocene corals from Southern New Guinea, and refers to the occurrence of corals with the Old Miocene limestone; and as he says these limestones include Alveolina they may be Eocene, but he does not describe the corals. The lists from Sumatra by Volz (1904, pp. 89, 90) include many species of corals from the Upper Pliocene, but none from the Eocene. The Miocene and Pliocene coral faunas are known from Java (Reuss, 1866, and Felix, 1913), Sumatra (Volz, 1904, p. 90), and from the collection by Dr. Andrews at Christmas Island (Gregory, 1900).
The nearest well-known fauna of Kocene reef corals is that described by Duncan (1880) from Sind. There is a certain generic resemblance between the two faunas, but some of the most typical of the Sind genera are absent from the New Guinea collection; and we have been able to refer only one of the New Guinea Kocene corals to previously known species.
The corals therefore strongly confirm the opinions of Martin (1915, p. 222) and Oppenheim (1901, p. 309) as to the remarkable isolation of the Eocene fauna of Malaysia. The presence of the
534 J. W. Gregory & Jean B. Trench—
Montipora is very significant in this connexion, for the Montiporids are unrepresented either in Sind or in Europe. A fossil Montipora has been recorded from the Pleistocene raised beaches of the Red Sea (Gregory, 1898, p. 117), and it would thus appear probable that the Montiporids originated in the Western Pacific, that they had not reached India even in Miocene times, and that they had reached the Red Sea in the Pleistocene.
REFERENCES.
D’?ARCHIAC. 1847. ‘‘ Extrait d’un Mémoire sur les fossiles des couches A Nummulites des environs de Bayonne et de Dax’’: Bull. Soc. géol. France (2), vol. iv, pp. 1006-15. \
—— 1850. ‘‘Descr. Foss. Numm. . . . aux environs de Bayonne et de Dax ’’: Mém. Soe. géol. France (2), vol. iii, pt. ii, No. 6.
BERNARD (H. M.). 1897. Catalogue of the Madreporarian Corals in the British Museum, vol. iii, pp. vii, 192, with 34 pls.
— 1906. Id., vol. vi, pp. iii, 173, with 17 pls.
BucKING (H.). 1902. ‘‘ Beitrage zur Geologie von Celebes’’: Samml. geol. Reich. Mus. Leiden (1), vol. vii, pts. i and ii, pp. 29-207, pls. iii-vii. — 1904. ‘* Zur Geologie von Nord- und Ost-Sumatra’’: ibid., vol. viii,
pt. i, pp. 101, with 6 pls.
DALTON (L. V.). 1908. ‘‘ Notes on Geology of Burma’’: Quart. Journ. Geol. Soc., vol. lxiv, pp. 604-44, pls. liv—lvii.
Dana (J. D.). 1848. United States Exploring Expedition during the years ' 1838, 1839, 1840, 1841, 1842, under the command of Charles Wilkes, U.S.N. Zoophytes, pp. vii, 740, with folio atlas of 61 pls.
DUNCAN (P. M.). 1880. ‘‘ A Monograph of the Fossil Corals and Aleyonaria of Sind, collected by the Geological Survey of India’’: Paleontologia Indica, ser. VII, vol. i, pt. ii, pp. 110, with 28 pls.
— 1885 (read 1884). ‘‘A Revision of the Families and Genera of the Sclerodermie Zoantharia, Ed. & H., or Madreporaria (M. rugosa excepted) ’?: Journ. Linn. Soc., Zool., vol. xviii, pp. 1-204.
EDWARDS (M.). 1860. Histoire Naturelle des Coralliaires ou polypes propre- ment dits, vol. iii, pp. 560.
Epwarps (M.) & HaAtmMeE (J.). 1848. ‘‘Note sur la classification de la deuxiéme tribu de la famille des Astréides ’’: C.R. Acad. Sci., vol. xxvii, pp. 490-7.
1850-4. A Monograph of the British Fossil Corals, pp. lxxxv, 322,
with 72 pls.
1851. Monographie des Polypiers Fossiles des Terrains Pal@o- Zotiques, précédée d’un Tableau Général de la Classification des Polypes, pp. 502, with 20 pls. (Archives du Muséum d’ Histoire naturelle, vol. v).
FELIX (J.). 1903. ‘‘ Verkieselte Korallen als Geschiebe im Diluvium v. Schlesien u. Mahren’’: Zentralbl. f. Min. 1903, pp. 567-70, with 2 text-figs.
—— 1906. ‘“‘Uber eine Korallenfauna aus der Kreideformation Ost- Galiziens’’: Zeit. deut. geol. Ges., vol. lviii, pp. 38-52, pl. iii.
— 1918. “Die fossilen Anthozoen aus der Umgegend yon Trinil”’: Paleontographica, vol. 1x, pp. 311-65, pls. xxiv—vii.
FritscH (K. yv.). 1875. ‘‘Fossile Korallen der Nummulitenschichten von Borneo ’’: Palaeontographica, Supplement III, pt.i: “‘ Die Hocanformation von Borneo und ihre Versteinerungen.’’? pp. 93-135, pls. xv-viii.
GERTH (H.). 1909. ‘‘Echte und falsche Hydrozoen aus Niederlindisch- Indien’’: Sitz. Niederrhein. Ges. Nat. Heil., Bonn, 1909, sect. A, pp. 17-25.
GREGORY (J. W.). 1898. ‘‘ A Collection of Egyptian Fossil Madreporaria ’’ : GEOL. MAG., N.S., Dec. IV, Vol. V, pp. 241-51, Pls. VITI-IX.
—— 1900. ‘‘On the Geology and Fossil Corals and Echinids of Somali- land’’; Quart. Journ. Geol. Soc., vol. lvi, pp. 26-45, with 2 pls.
Eocene Corals, Central New Guinea. | Bas)
GREGORY (J. W.). 1900. ‘‘ The Fossil Corals of Christmas Island.’? In C. W. Andrews’ Monograph of Christmas Island, pp. 206-25.
—— 1900. ‘* The Corals.’’ Ser. 1x, vol. ii, pt. ii, of The Jurassic Fauna of Cutch. Pal. Indica, Mem. Geol. Sury. India, pp. iii, 195, ix, pls. iia— XXvii.
— 1906. ‘‘On a Collection of Fossil Corals from Eastern Egypt, Abu Roash, and Sinai’’: Grou. MaG., Dec. V, Vol. III, pp. 50-8, 110-18, Pls. VI, VII.
JACK (R. J.) & ETHERIDGE (R., jun.). 1892. The Geology and Paleontology of Queensland and New Guinea, pp. xxi, 768, 1 vol. of 68 pls., 1 map separate.
JACK (R. L.). 1894. Reports by Messrs. R. L. Jack and W. H. Rands on Geological Specimens: Ann. Rep. Brit. New Guinea from July 1, 1893, to June 30, 1894 (S. 26-9601), Appendix BB, pp. 91-6.
MACGREGOR (W.). 1890. Despatch giving details of an expedition undertaken to explore the course of the Fly River and some of its affluents: Ann. Rep. Brit. New Guinea from July 1, 1889, to June 30, 1890 (C.A. 105-1890), Appendix G, pp. 49-64, with 1 map.
MAITLAND (A. GIBB). 1893. ‘‘ Geological Observations in British New Guinea in 1891’: Ann. Rep. Brit. New Guinea from July 1, 1891, to June 30, 1892 (A. 1-1893), Appendix M, pp. 53-85, with 3 maps and 3 pls.
MARTIN (K.). 1879-80. Die Tertidirschichten auf Java: Corallia, pp. 132-50, pls. xxiv—vi; Leiden.
— 1881. ‘‘Hine Tertiarformation von Neu-Guinea und benachbarten Inseln’’: Samml. geol. Reich. Mus. Leiden, vol. i, pt. ii, pp. 65-83, pl. iii.
— 1900. ‘*‘Die Hintheilung der Versteinerungs-Fiihrenden Sedimente von
' Java’: ibid., ser. I, vol. vi, pp. 135-245.
—— 1911. ‘‘ Palaéozoische, mesozoische, und kinozoische Sedimente aus dem sudwestlichen Neu-Guinea’’: ibid., vol. ix, pp. 84-107, pl. viii.
—— 1915. ‘*‘Die Fauna des Obereocéns von Nanggulan auf Java’’: ibid., N.S., vol. ii, pt. v, pp. 179-222, pls. vii, viii.
MICHELIN (H.). 1840-7. Iconographie Zoophytologique, pp. xii, 348, vol. of 79 pls.
NEWTON (R. B.). 1916. Notes on some Organic Limestones, etc., collected by the Wollaston Expedition in Dutch New Guinea. LHxtract from “Reports on the Collections made by the British Ornithologists’ Union Expedition and the Wollaston Expedition in Dutch New Guinea, 1910-137’, vol. ii, Rep. No. 20, pp. 20, with 1 pl.
OGILVIE (M.M.). 1896. ‘‘ Microscopic and Systematic Study of Madreporarian Types of Corals ’’: Phil. Trans. Roy. Soc., vol. 1878, pp. 83-345.
OPPENHEIM (P.). 1901. ‘‘ Die Priabonaschichten und ihre Fauna, im Zusammenhange mit gleichalterigen und analogen Ablagerungen vergleichend betrachtet’’: Paleontographica, vol. xlvii, pp. 348, with 21 pls.
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Reis (O. M.). 1890. ‘‘Die Korallen der Reiter Schichten’’: Geognotische Jahreshefte, vol. ii, pp. 91-162, with 3 pls. ;
Reuss (A. H.). 1866. ‘‘ Uber fossile Korallen von der Insel Java’: Reise Ost. Fregatte Novara, Geol., vol. ii, pt. ii, pp. 163-85, with 3 pls.
— 1870. ‘‘ Oberoligociine Korallen aus Ungarn’’: Sitz. k. Akad. Wiss. Wien., vol. lxi, pt. i, pp. 37-56, with 5 pls.
RUTTEN (L.). 1914. ‘‘ Foraminiferen-Fuhrende Gesteine von Niederlandisch Neu-Guinea’’: in A. Wichmann’s Nova Guinea, vol. vi, liv. ii (Géologie), pt. ii, pp. 21-51, pls. vi-ix.
SCHUBERT (R.). 1910. ‘‘ Uber Foraminiferen und einem Fischotolithen aus dem fossilen Globigerinenschlamm von Neu-Guinea’’: Verhandl. k.k. Geol. Reichs., pp. 318-22.
THOMSON (J. P.). 1892. British New Guinea, pp. 336, with map and 9 pls.
536 R. Mountford Deeley—The Ice Age
TORNQUIST (A.). 1901. ‘* Uber mesozoische Stromatoporiden’’: Sitz. k. preuss. Akad. Wiss., pt. ii, pp. 1115-1123.
TRAUTH (F.). 1911. ‘‘ Die Oberkretazische Korallen-Fauna von Klogsdorf in Mihren’’: Zeit. Mahr. Landesmus., vol. xi, pp. 104, with 4 pls.
Vouz (W.). 1904. ‘‘ Zur Geologie von Sumatra’’: Geol. Pal. Abh., Jena, vol. x, pp. 87-196, with 12 pls.
Wo.uaston (A. F. R.). 1914. ‘‘ An Expedition to Dutch New Guinea”’ : Geogr. Journ., vol. xliii, pp. 248-73, with 3 pls. and map (p. 364).
EXPLANATION OF PLATES XXI-XXII. PLATE XXI.
1. Actinacis swmatraensis (Tornquist). No. 14. Part of transverse section of corallum, x 6 diam.
2. A. maitlandi, n.sp. No. 20. Fig. 2a, part of transverse section of corallum, x 6 diam.; Fig. 2b, part of polished surface of corallum, horizontal section, x 6 diam.
3. A. maitlandi, n.sp. No. 37. Part of transverse section of corallum, x 6 diam.
4. Kobya hemicribriformis, n.sp. No. 35. Part of polished surface of corallum, nat. size.
PLATE XXII.
1. Montipora antiqua, n.sp. No. 36. Fig. 1a, part of polished surface of corallum, horizontal section, x 3 diam.; Fig. 10, part of polished surface of same specimen, vertical section, x 3 diam.
Porites deshayesana, Mich., var. wmequisepta, n.var. No. 23. Fig. 2a, part of surface of corallum, x 10 diam.; Fig. 20, part of surface of corallum, x 23 diam.
The locality of all the specimens is the Upper Fly River, New Guinea. The species figured are from the Eocene, and probably Middle Eocene, except Actinacis sumatraensis, which is Upper Cretaceous.
NoTE.—Since the first part of this paper was printed we have received from Mr. F. Chapman a description of Aquitanian limestones with Lepido- cyclina and Heterostegina, which were collected at Bootless Inlet, British New Guinea, by Mr. J. E. Carne (Chapman, F. 1914. Description of a Limestone of Lower Miocene Age from Bootless Inlet, Papua. Journ. Proc. Roy. Soc. N.S. Wales, vol. xlviii, pp. 281-301, pls. vii—ix).
November 17, 1916.
bo
IJ.—Tue Cavsze or rae Ick Acr anp Guacter Frucrvations. By R. M. DEELEY, M.Inst.C.H., F.G.S.
({\HE fluctuations which take place from time to time in the lengths
of glaciers are extremely interesting to the glaciologist; for there are good reasons for believing that the meteor ological conditions which give rise to the lesser oscillations of glaciers are generally of the same character as those which produced the great secular changes of climate which occurred in past ages.
At the present time there are no theories purporting to account for the more important glacier fluctuations. The one assumes that they are due to increased precipitation per square yard, whilst the other attributes the phenomena to a general lowering of the tempera- ture of the atmosphere, the precipitation per square yard remaining practically unaltered. Iu the case of the latter theory, the variation in the amount of ice formed is considered to be due to the lowering of the snow-line and consequent increase in the size of the mévé areas.
It is evident that within historic times changes of climate have occurred, for we have records of very considerable advances and
Grot. Maa., 1916. XXII.
tis. Pio “BESS
Photos by S. Fingland, Gregory & Trench. EOCENE CORALS, NEW GUINEA.
Montipora. Porites.
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and Glacier Fluctuations. 5387
retreats of glaciers in many parts of the world, whilst during Pleistocene time very much more pronounced oscillations are known to have taken place. ‘he question asto whether the prehistoric great. oscillations of climate, and the less pronounced historic oscillations, have been due to similar climatic changes is one of considerable interest. That glacialists are by no means all of one opinion on this point may be gathered from the recent literature of the subject.
The very existence of glaciers depends upon both temperature and amount of precipitation ; for the presence of glacier ice results from the fact that over certain areas more snow falls in the winter than the summer heat can melt, and as the ice thus collected is a very viscous liquid it slowly flows to lower levels and reaches altitudes where the temperature is sufficiently high to melt it. In glaciers we thus always have alimentation and ablation areas.
Within the limits of height reached by mountains, as we rise in the atmosphere, the temperature falls, and as a glacier is ascended the temperature falls about 1° C. for every 140 metres of vertical rise.! On this account a greater proportion of the precipitation comes down as snow at high levels than is the case at lower levels. However, the precipitation per square yard varies considerably with the height and aspect of the mountain mass. ‘Thus it has been shown that on the declivities of the Aiguille du Gouter the precipitation falls off rapidly as we ascend or descend from the level of 2,550 metres. Indeed, the precipitation not only varies greatly from place to place on a mountain range, but when the precipitation is in the form of snow it is blown to great distances, or slides off the slopes and collects at low levels in great masses. In the Northern Hemisphere, slopes and valleys facing south are much more exposed to the sun’s rays than are those having a northerly aspect, and the winds reaching them are generally warmer. ‘There is, consequently, no regular continuous snow-line, i.e. a regular level above which some of the winter snow survives the heat of summer and below which all the snow of winter is melted away during the summer.
Although the snow-line is a very irregular feature as regards height, in the case of the majority of glaciers it will be found that
‘snow-lines can be drawn across them and their tributaries, above which some of the snow of winter does not entirely melt each year, and below which not only is all the snow melted away but some of the ice is melted as well. Such a snow-line cuts the glacier into two portions, of which the upper portion is the alimentation area, whilst the lower portion is the ablation area. Ifthe meteorological conditions remained invariable from year to year, then the glacier would always appear to be in the same condition during the corresponding months of each year.
If the precipitation of snow should increase per square yard, then the snow-line would be lowered, the névé would get thicker and larger in area, and as a result the ablation area of the glacier (the tongue portion) would have to grow longer, and if possible wider, so as to admit of the greater quantity of ice coming down being melted
1 Hans Hess, Die Gletscher, 1904, p. 210.
538 R. Mountford Deeley—The Ice Age
away. On the other hand, if the total precipitation per square yard remained unaltered, and the snow-line were lowered owing to a colder atmosphere, then the snow collected in the larger névé (alimentation area) would be greater in quantity and the ablation area would have to be increased by the lengthening and broadening of the tongue (ablation) portion.
The Figure is a map of a small glacier showing the snow-line. A is the alimentation area, and B is the ablation area. These two areas of any glacier must be properly proportioned the one to the other.’ Taking a large number of glaciers the average area of the alimentation region is about three times that of the ablation region. A comparatively small change in the position of the snow-line, in the case of such a glacier as is shown in the Figure, would cause a considerable retreat or advance of the glacier tongue.
Map of a small glacier showing (A) the alimentation area and (B) the ablation area.
Although it is clear that either of the theories here considered explains how glacier variations may occur, they are so fundamentally different in principle that it is of the utmost importance that they should both receive very careful consideration when dealing with glacier fluctuations, large or small. They may be referred to as the precipttation and temperature theories respectively.
Any increase in the precipitation per square yard requires an increased rate of evaporation over the water-covered areas, and to obtain this a hotter sun is required. Such an increase of temperature would tend to raise the snow-line, whilst the increased precipitation of snow would tend to lower it. On this point? Tyndall remarks:
1 Die Gletscher, 1904, p. 84. 2 Heat considered as a mode of motion, chap. vi.
and Glacier Fluctuations. 539
‘‘ So natural was the association of ice and cold, that even celebrated men assumed that all that is needed to produce a great extension of our glaciers is a diminution of the sun’s temperature. Had they gone through the foregoing calculations they would probably have demanded more heat instead of less for the production of a glacialepoch. What they really needed were condensers sufficiently “powerful to congeal the vapour generated by the heat of the sun.’ According to the temperature theory the condensers which Tyndall demands are furnished by the increased areas over which the whole of the snow- fall does not melt each year, these increased areas being produced by the fall of the snow-line as a result of lower atmospheric tempera- tures. The precipitation in the Glacial period may have been rather less per square yard than it is now; but this was more than made up for by the increase in the size of the alimentation areas. Paschinger! is of opinion that the determining factor in the height of the snow-line is above all the temperature of the air, and as a result of the study of the precipitation and temperature of the earth he considers that, in general, both in the longitudinal direction and in the latitudinal direction the influence of warmth on the height of the snow-line is greater than that of precipitation. He shows that in the Swiss Alps the snow-line is much higher on the warm south side than it is on the colder north side.
There is one important consideration which has caused many to reject the precipitation theory as an explanation of the glaciation of Switzerland. In the Swiss valleys one can often see where the upper limit of the old ice-fields stood. Below the limit the rocks are more or less smoothed and levelled; above they are broken and craggy. If such a valley has glaciers and snow-fields at its source, it will be noticed, as one passes up the valley, that the craggy ridges are continuous with these that rise above the neve, and that the névé abuts directly against them. There are no ‘signs in these elevated regions that the névé was ever thicker than it is now; and the view taken is that during the Glacial period the névé-covered region was greatly extended in area, but that the higher regions then presented much the same appearance they do now. Had the snow- fall in the past been much greater than it is at present, signs of thicker ice and névé would now be visible at the higher as well as the lower levels.
The more carefully the question of the cause of glacier advances and retreats has been studied in the field the more certain it has appeared that all considerable glacier fluctuations have been due to fall of temperature, accompanied, perhaps, by a slight decrease in the precipitation per square yard. Much more snow is converted into ice, but this has been due to the greater area over which it did not entirely melt. Thereis good reason to believe that in Switzerland the snow-line was so low in the Glacial period that even the great mass of ice which covered the region of Lake Geneva rose share its and that, therefore, the whole of the Rhone Glacier trunk, and
Peterman’s Mitteilungen, i, pp. 57-60, 1911, and Pet. Mitt. Ergangungsheft, No. 173, Gotha, 1912.
540 R. Mountford Deeley—The Ice Age
a great portion of the piedmont it formed, were alimentation areas. The ice had to spread as far as Lyons before a sufficiently large ablation area could be formed to enable the warm air and rain of the lower regions to melt the ice completely.
Penck & Bruckner’ express themselves to the following effect : ‘“The Alps during the Ice Age appeared essentially different to the Greenland of to-day. They bore no inland ice. In the interior of the mountains there was no continuous névé field. The individual glaciers were very similar to those of the present day—widely separated from one another by mévé ridges, which are not to be compared with the nunataks of Greenland. The ice-stream network showed, therefore, a similar slope development to the Greenland inland ice; it formed in the middle a smooth arching shield, which became steeply bent at the margin. But above this shield still rose the névé ridges, in the North Tyrol by about 1,000 to 1,500 metres, in Switzerland in places by about 2,000 or even 2,500 metres, and from these névé ridges separate glaciers sank down to the ice-stream network, usually with extreme steepness, but at times with gentle gradient. The Ice Age glaciers displayed a swelling of the tongues, but not at the same time a swelling of the névé fields of the present glaciers. Now if during the Ice Age the névé fields were no fuller than now, we cannot ascribe the glacier development during the Ice Age, compared with that of the present day, to an increase in precipitation, but must trace it to a decrease of ablation.”
The question of the climatic conditions of the Ice Age will be found to have been very fully discussed by Penck & Bruckner as far as the Alps are concerned. They are decidedly of opinion that the phenomena exhibited in this area show that the Ice Age was essentially one of low temperature, not of increased precipitation. They conclude that at the culmination of the Glacial period the snow-line stood at an altitude of 1,200 metres below the present snow-line, and that the frost period at this low level was of equal duration to that which exists at the present snow-line. Such a fall of the snow-line would enormously increase the alimenta- tion areas.
From a comparison of the Ice Age snow-line with that of the present day Penck & Bruckner also conclude that the general winds of the Ice Age blew, as regards direction, much as they do now, for, from the close relationship between the height of the snow-line during the Ice Age and the present distribution of precipitation, they hold that during the Ice Age a similar distribution of precipitation existed as at the present day; that in particular also at that time the rain- bringing wind was the west wind, and that the ‘adria’ bestowed on the south-east angle of the Alps abundant precipitation.
At the present time the snow limit, although of variable height on the same latitude, is higher in the Tropics than it is in the Frigid regions. But it is also often lower where the precipitation is greatest. Thus we have in the Andes a lower snow-line where the precipitation is greatest. North and south of this point the snow-line
1 The Alps in the Ice Age, p. 1141 et seq.
and Glacier Fluctwations. 541
rises, but as we go further north or south the effect of latitude begins to tell, and the snow-line falls rapidly as the Polar areas are reached. However, even in the Polar areas, the snowfall is often so small in many districts that it is all evaporated or melted by the summer sun.
A change in the direction of the winds, and, therefore, of the areas of greatest precipitation, might cause some of the present glaciers to disappear and fresh ones to appear in other places, but it ‘ could scarcely cause intense glaciation over large areas which are now free from ice. The greater prevalence of northerly winds in the Northern Hemisphere would lead to drier conditions there, and if such occurred British Columbia, Alaska, and Greenland would be less ice-covered than at present. But the Ice Age does not appear to have been either due to an alteration of any note in the direction of the winds, or to any notable increase in the precipitation.
Tutkowski has maintained that dry conditions existed at the edges of ice-sheets owing to cold winds blowing off them. That this has been the case is very likely, but here we are only dealing with local effects, the precipitation being decreased outside the margins of the ice-sheets and increased to a like extent on the ice- sheets themselves.
With regard to the greater glacier advances which brought the ice down on to the lowlands in many continental areas, W. B. Wright? takes the view that it is to change of temperature, and not increased precipitation, that we owe the Ice Age. Some other glacialists do not seem to be of this opinion, for quite recently it has been main- tained that the minor oscillations are due to increased precipitation.
As far as can be judged from the evidence of glacial moraines, ete., it would appear that even the greater advances and retreats of ‘the glaciers in Pleistocene time did not take place in a regular manner. ‘lhe ice margins appear to have always advanced or retreated in an irregular way. The moraines formed during the retreat of the ice-sheets show this most clearly. These moraines lie one behind the other, each moraine showing where the ice rested for a time, or where a temporary advance stopped. It might be urged that the greater oscillations are due to one kind of climatic variation, whereas the smaller oscillations are due to another kind. Indeed, it would appear that in some quarters the greater variations are considered to be due to changes of temperature and the smaller ones to precipitation changes. But it is impossible to divide the glacier fluctuations into two groups, the large and the small. Glacier variations are of all magnitudes, and it appears to be more reasonable to regard all glacier fluctuations, except perhaps some of the annual or very inconsiderable ones, as being due to fall of temperature.
That neighbouring glaciers very often do not advance and retreat together is often difficult to explain. Throughout any particular region, however, where there are a large number of glaciers, the majority of them move in close agreement the one with the other.
! The Quaternary Ice Age, p. 146.
542 E. M. Kindle—Pit and Mound Structure.
IiL.—Smatt Pir ann Mounp SrrucrurEs DEVELOPED DURING SEDI- MENTATION!
By EK. M. KINDLE. (PLATE XIII.) IntrRopUcTION.
EDIMENTARY rocks show a variety of minor structures whose k-) origin has been obscure. Among these are the small circular pits and mounds which sometimes mark the surfaces of sedimentary strata. Such of these as cannot be referred to rain-prints or the work of worms are apt to be referred by the geologist to some obscure type of concretion.
Since the publication of Lyell’s? excellent description of recent and fossil rain-prints most of the small shallow pits and mound- shaped protuberances met with on the surface of stratified rocks have been ascribed to the work of raindrops. Lyell in describing rain- priits mentions also certain small protuberances resembling rain- print casts on dried ripples of mud from the Bay of Fundy, which Faraday duplicated Gaia iene by introducing air into the lower part of a tube of mud. These on bursting gave cavities resembling in size the ordinary rain-prints, but in nearly all cases without any rim projecting above the general surface as in rain-prints. |
In the present paper it is proposed to describe processes of sedi- mentation observed under laboratory conditions which result in the formation of miniature pits or mounds at the top of chimney-like tubes in the falling sediment. Some of these are comparable with raindrop impressions and may have been frequently mistaken for rain-prints when met with in consolidated rocks. It is believed too that the processes observed in the experiments to be described should be given consideration as possible factors in the explanation of certain types of concretions.
The experiments on which this paper is based illustrate an important serie: of phenomena attendant upon sedimentation which are allied to. if not identical with, those known to chemists under the general term catalysis. These include changes in water, suspended sediment resulting in flocculation and deposition, which are brought about by the presence of agents which themselves remain stable and are not precipitated. In other words, the active or predisposing agent does not unite with the precipitate. Professor Brewer,? who was one of the first to investigate this subject, found that very fine sediment may remain in suspension for as much as six years when left undisturbed in fresh water, while the same sediment might be precipitated in a few minutes in sea-water. With some clays the precipitation is as much in thirty minutes in salt water as it is in as many days or months with fresh water. A considerable amount of
1 Published with the permission of the Director of the Geological Survey of Canada.
2 “On Fossil Rain Marks of the recent Triassic and Carboniferous Periods”? : Quart. Journ. Geol. Soc. vol. vii, pp. 238-47, figs. 1-8, 1851. :
3 Wm. H. Brewer, ‘‘ On the Subsidence of Particles in Liquids’’ : Memoirs Nat. Acad. Sci., vol. ii, pp. 163-75.
Geox. Maa., 1916. PuatTE XIII.
Fic. 1a.
MG, Be Fic. 1B.
Fias. 14 and 18.—Pit and mound-structures developed in sedimentation. Fic. 2.—Impressions of rain-drops from Bay of Fundy.
E. M. Kindle—Pit and Mound Structure. 543
experimental work has been done on this subject by Reade and Holland.! They have tried a large variety of fine clays. From these standard turbidity preparations of water were prepared in which weight of fine clay ina given volume was known. To these were added as precipitants in their experiments: (1) sea-water, (2) calcium dicarbonate, and (8) calcium sulphate. Equal volumes of precipitant and muddy water were mixed, and time of flocculation and complete clearing noted. Flocculation was always far more rapid than in the case of untreated water. The work of these and other authors has clearly shown the effect of salt and other constituents of marine waters in accelerating sedimentation.
In the following experiments, which were made at air temperatures with the fine-grained blue Pleistocene clay of the Ottawa Valley, attention will be directed to the action of the vertical currents which are developed during the deposition of clay sediment in the presence of salt.
EXPERIMENTS.
Two quarts of water were thoroughly mixed with 8 cubic inches of clay and placed in two milk bottles of quart size with flaring type of neck. I'wo tablespoonfuls of salt were mixed with one (A), the other (B) remaining a freshwater mixture. At the end of ten minutes the flocculated clay in A had settled 24 inches, and the upper 21 inches of the mixture was clear enough to read fine print through neck of bottle. In ten minutes the sediment had settled 43 inches, the mixture being perfectly clear in the upper part. The fresh- water mixture showed no clearing during this interval. The settling was accompanied by constant upward currents of sediment all round the sides of bottle, starting from the contact of the flared and straight- sided part of the bottle. After the top of sediment had settled to the level of the straight-sided portion of bottle these upward currents on the sides ceased, and the surface of sediment at this stage was covered over by small fumarole-shaped mounds, 3 to 10 mm. in diameter, each with an opening at the summit the size of a pin-head or smaller. The B mixture showed no sign of clearing during this period. Eighteen hours after starting this experiment 2 inches of sediment had fallen to the bottom of A, and the liquid above was perfectly clear. The sediment still had the irregular miniature-mound covered surface noted above. No settling appeared to take place in B during this time. After forty hours, settling had nearly ceased in the saline mixture, leaving perfectly clear water above the 2 inches of sediment. The freshwater bottle showed its original turbidity throughout. Another freshwater mixture of this clay remained turbid after standing 21 months. At the end of forty hours the saline mixture was thoroughly shaken and sedimentation started over again. The phenomenon noted above was repeated as already described, except that the process was slightly more rapid than in the first case.
In order to test the effect of the shape of the containing vessel on the production of the ascending currents noted above around the sides
1. M. Reade & P. Holland: ‘‘ Sands and Sediments,’’ Pt. I: Proc. Liver- pool Geol. Soc., vol. x, pp. 48-78, 1906.
544 E. M. Kindle—Pit and Mownd Structure.
of the vessel, another clay mixture in water was prepared, and placed in an ordinary table glass with vertical sides. The mixture was left to settle after adding a level teaspoonful of salt. After two hours the suline mixture showed at the top 12 inches of perfectly clear water, while another glass with a duplicate mixture, but without salt, showed no indication of clearing. This experiment gave no indication of the ascending currents along the sides of the glass seen in the bottle, hence the strength of these currents in the bottle must be ascribed to the shape of flaring neck expanding downwards. In the glass as in the bottle, however, the chimney-lke tubes opening into miniature craters and mounds were developed over the surface. But instead of being uniformly distributed over the surface as in the bottle, they were grouped around the sides of the glass and near the centre of the surface of the sediment. The largest one had a diameter of #inch. Observation of the pin-hole openings in the centre of each of these tiny structures showed ascending currents of water which could be recognized by occasional particles of sediment coming up through them. After fifteen hours the upper 22 inches of the glass was perfectly clear. The other glass was opaque from the top down, showing no evidence of the beginning of settling.
In order to further study the action of the upwelling currents which produce the small mounds and pits on the surface of the subsiding sediment another mixture of the clay and water to which a small quantity of salt had been added was placed in a tube, 30 X inches. The tube affords the best possible means of observing the strong upwelling current action developed in a mass of subsiding sediment if it is set in a position inclined a few degrees from the vertical. Instead of the numerous miniature currents which would develop if left in a vertical position a single strong current then develops on the upper side of the tube, which carries upward a steady stream of the small particles of sediment. The current is apparently the resultant of the gradual downward movement of the whole subsiding mass of sediment in the upper part of the tube. This mass had subsided 14 inches in about 13 hours. Intwo days it had subsided 204 inches. On the third and fourth days subsidence amounted to only 1 inch, and then dropped to 4 in. per day for two or three days before becoming imperceptible. These currents belong apparently to the class of phenomena called convection currents,’ although there is no noticeable temperature difference between the upper and lower parts of the mixtures in which they are produced. In some cases the current builds a mound-shaped mass about the mouth of the tube ; in others a circular pit with a rim about the margin develops instead of the mound. Sometimes, instead of either of these, pin-head depressions appear over the surface. Beehive- shaped protuberances with a small opening at the top are the most common. The appearance of the peculiar surface which is developed on a precipitate in which salt is the accelerating factor in throwing down the sediment is shown in Figs. 14 and 8. The clay mixture shown in this Figure was placed in a vessel 63 inches deep, which it filled and
1 Robert B. Sasman, ‘‘ Types of Prismatic Structure in Igneous Rocks ”’ : Journ. Geol., vol. xxiv, p. 219, 1916.
/
EH. M. Kindle—Pit and Mound Structure. 545
photographed after settling two hours. Half of the same mixture after being shaken was placed in a vessel 10 X 6 inches, and allowed to settle in order to see how the increased lateral extent and decreased (4 in.) depth would affect the currents in the body of the mixture and the resulting surface features. In this shallow vessel only a few small and poorly developed vents appeared.
SuMMARY AND Discussion.
The experiments which have been described show that sedimentation in salt water, when very fine sediments like mud are involved, is accompanied by the development of vertical currents. Parallel experiments with fresh water showed no evidence of this phenomenon. These upwelling currents keep open vertical tubular channels through the subsiding sediment, and develop in some cases around the mouths of their upper extremities shallow pits, somewhat resembling in outline raindrop impressions, but differig through lacking the sharply defined rims which characterize rain-prints (Fig. i) “Under certain conditions these vertical currents, instead of ending in shallow basins, build up around their upper terminals mound or chimney-like protuberances which have the appearance of small concretions or the work of burrowing invertebrates. Under natural conditions these vertical currents would probably be effective in developing surface features on the sediments only where deposition was very rapid, as in the delta area of a large river. Where the deposition of mud is going on at the rate of 12 inches in four days, as has been reported on parts of the Gulf coast, the features which have been described would be very likely to be developed. It is quite possible that the structures described when developed under marine conditions would be much larger than any which can be produced under laboratory conditions. Certain curious funnel-shaped depressions which were observed by Mr. L. D Burling and myself on a mud-bar in one of the Bay of Fundy estuaries, near Truro, N.S., are believed to belong to this class of phenomena. The largest ‘of these depressions were 19 inches wide and 4 inches deep, while the smallest were about one-fifth of this size. At the time they were examined the origin of these very regular funnel-shaped pits was a puzzle to both observers.
The vertical tubular canals which are developed under the conditions which have been described would doubtless be closed in nearly all cases by the pressure of the adjacent sediment as soon as the ascending currents ceased. The small pits or mounds which are formed about the upper ends of these channels would, however, remain at least for a time, and under favourable conditions might be preserved as permanent features on the surfaces of the strata. The courses of the vertical canals, although partially or completely closed, might remain the routes of maximum movement of waters percolating through the sediments for an indefinite period. When such waters carried with them and deposited mineral matter, vertical concretions cylindrical in section like the remarkable log-like
1 Louisian Gulf Biological Station Bull. 3, p. 28, 1905. DECADE VI.—VOL. III.—NO. XII. 35
546 E. M. Kindle—Pit and Mound Structure.
concretions' in the Potsdam sandstone near Kingston might be developed.
[ Norr.—Fig. 2 (added by the Editor to this Plate) has been repro- duced from a photograph faken direct, by the kind permission of Dr. A. Smith Woodward, the Keeper of the Geological Department of the British Museum (Natural History), Cromwell Road, London, from one of the original dried slabs of reddish mud, presented by Sir Charles Lyell from the Bay of Fundy, Nova Scotia, which are still carefully preserved in the Geological Gallery, and were described by Lyell in his paper ‘“‘On Fossil Rain- marks of Recent ‘Triassic and Carboniferous Periods’, April 30, 1851 (see Quart. Journ. Geol. Soe., vol. vii, pp. 288-47. See also woodcut, p. 240), where he writes: ‘‘The finest examples sent to me from Kentville (Bay of Fundy) were made by a heavy shower which fell on July 21, 1849, when the rise and fall of the tides were at their maximum in that small estuary which opens into the Basin of Mines. The impressions [see owr reproduction Pl. XIII, Fig. 2] consist of cup-shaped or hemispherical cavities, the largest being fully half an inch in diameter, and from one-tenth to one-sixth of an inch deep; but there are very few of such dimensions. The depth is chiefly below the general plane of stratification, but the walls of the cavity consist partly of a prominent rim of sandy mud, formed of the matter which has been forcibly expelled from the pit, and this margin or lip sometimes projects as much above the plane of the stratum as the bottom of the pit extends below it. The rim of the largest rain-prints is sometimes no less than one-twelfth of an inch broad, but it is usually much narrower. ‘The outer side of it is often perpendicular or almost overhanging. . . . All the cavities having an elliptical form are deeper at one end, where they have also ahigher rim, and all the deep ends have the same direction showing towards which quarter the wind was blowing. Two or more drops are sometimes seen to have interfered with each other, in which case it is usually possible to determine which drop fell last, its rim being unbroken. ... ” Lyell adds a note to his paper: ‘‘ Since the above was in type, my attention has been called toa notice by Dr. Buckland? ‘On Cavities caused by Air Bubbles on the Surface of Soft Clay’, which he justly observed ‘must be carefully distinguished from impressions made by rain’ ”’.
As bearing upon the present paper, we may draw attention to a Plate (Pl. IV, Vol. II, Guor. Mac., 1865, p. 137), reproduction of markings on the surface of a. slab of Carboniferous Sandstone from Bishop Auckland, described by Mr. J. Duff. Also suggested. explanation by Mr. Alexander Bryson, accompanied by a text- diagram figure (Grot. Mac., 1865, pp. 188-91), in which the writer shows that these horseshoe-like markings are in.all probability to be attributed to the heaping up of grains of sand against the windward side of the burrows of the common sandhopper ( Zalitrus saltator), the
1 N.Y. State Mus. Bull. 145, pl. xiii. * Reports of British Association, 1842, Trans. Sect., p. 57.
Dr. A. Wilmore—The Northern Pennines. 547
moisture of the burrow causing the grains to adhere and dry in a crescent-shaped form around the margins. After the surface- markings have dried and slightly hardened, dry dust or sand must blow over them before a fresh tidal deposit flows over and entombs them to form a problem for some future geologist to puzzle over.— Ep. Gon. Mace. |
EXPLANATION OF PLATE XIII.
Fie. 1la.—Circular impressions developed on the surface of water-laid sediment by vertical currents.
16.—Part of the same surface seen in Fig. la, rather more enlarged.
2.—Photograph of part of a slab from the Bay of Fundy (see supra, p. 546).
29
99
I1V.—A Sxercu oF THE SrrRucrure oF THE NorrHeRN Pennines.! By Dr. A. WILMORE, F.G.S.
f{\HIS paper attempts a brief summary of the structure of the
Northern Pennines for geologists and geographers, especially for those who are interested in the relation of geographical form to geological structure. It is, for the most part, a re-statement, and advances little that is new; but it is thought that the present visit of the Association to the North may be a fitting opportunity to summarize our knowledge of the structure of an interesting region, especially as considerable progress has been made in our detailed knowledge of the Northern Pennines since the visit of the Association to Newcastle in 1889.
By the ‘‘ Northern Pennines” as treated in this paper, we mean that well-defined part between the two great gaps—the Tyne Gap and the Craven or Aire Gap. Im this part of the Pennines the mountain masses are broader and higher, and the structure is some- what different from that of the Pennines south of the Craven Gap. The familiar anticline is not so conspicuously developed as in the southern half of the Pennines.
In the Northern Pennines the student may see very clearly indeed the broad dependence of the topography upon rock-character, rock- position, and geological history.
The Craven or Aire Gap may be taken as a convenient starting- point. This is a lowland region of roughly triangular form drained by four local river systems: the Wharfe, the Aire with Broughton Beck, the Ribble with the Lancashire Calder, and the Wenning (one of the feeders of the Lune). Each of these outlets of the ‘gap’ is utilized by a railway. The Leeds and Liverpool Canal follows the valleys of the Lancashire Calder and the Aire, and crosses the Pennines at an elevation of a little over 500 feet (the highest point is at Foulbridge Tunnel, near Colne).
The Middle Pennine Gap is determined by the great Craven Fault system and the folding of the strata to the south and south-west of
~ the fault. The general direction of the folding is from W.S.W. to
1 Read before the British Association, Section C (Geology), Newcastle, 1916.
548 Dr. A. Wilmore—The Northern Pennines.
E.N.E. Near the Fault there is considerable and somewhat intense local folding, and probably some repetition of the beds.
North of the Craven Gap, and stretching to the Tyne Gap, is the Plateau, or Block country—the Northern Pennines of this paper— determined mainly by the three great western fault systems; these are the Pennine, the Dent, and the Craven Faults. Three ‘blocks’ of the Northern Pennines are thus formed: (1) the Cross Fell block, (2) the Mallerstang or Dent block, (3) the Ingleborough-Penygent block. On these plateau blocks the mountains stand, excellent examples of mountains of circumdenudation or residual mountains. Ingleborough or Penygent may be taken as a type of these mountain masses, standing on the plateau floor of the Great Scar Limestone and capped by outliers of Millstone Grit. The Great Scar Limestone is gradually replaced towards the north by the coming in of the Bernician type. The Great Scar Limestone of the Penygent block is a region famous for pot-holes and underground streams, such pot- holes as Gaping Ghyll and Alum Pot being well known. On the great plateau numerous streams disappear to reissue in the valleys below, frequently at the unconformity where the limestone, with or without its basement conglomerate, lies almost horizontally on the upturned edges of the Older Paleozoic rocks.
These plateau blocks are not all similarly related to the adjacent westerly regions. On the east of the great Pennine Fault is the wedge-shaped Vale of Eden, filled with Permian and Triassic strata. There is an interesting inlier chiefly of Older Paleeozoic rocks occurring between the Carboniferous plateau block and the New Red beds of the plain. This is known as the Cross Fell inlier, and is characterized by a series of magnificent ‘pikes’, like a narrow strip of the Lake Country tacked on to the western edge of the Pennines. This inlier stretches from near Brough in the south to Melmerby in the north. The Dent Fault has its downthrow to the east, and along the complex fault-line the Carboniferous Limestone is in contact with the Older Paleozoic rocks of the Howgill Fells and the moors to the north and north-east of Kirkby Lonsdale. The Carboniferous block to the east of this fault is the Mallerstang block of this paper. It is remarkable for the great number of mountain masses which rise to between 2,000 and 2,400 feet. An eastern part of this block is the original region of the Yoredale of Professor Phillips ( Wensleydale is Yoredale or Uredale). The Craven Fault system throws the Carboniferous Limestone, chiefly the Great Scar Limestone, against Permian, or Coal-measures, or Millstone Grit, or the higher divisions of the Carboniferous Limestone itself.
To the geographer the change of scenery in crossing these faults is most interesting. The view from the western limestone scars of the Cross Fell block across the Vale of Eden to the Lake District mountains is one of the finest in Britain. The change from the Older Paleozoic Howgill Fells, Grayrigg Fells, Middleton and Barbon Fells eastward across Garsdale or Dentdale to the Carboniferous Fells of the Yoredale country of Mallerstang is, perhaps, not so striking but is yet very marked. The change from the Penygent block—with its great plateau floor, its step-like Yoredale mountains, capped with grits,
Dr. A. Wilinore—The Northern Pennines. 549
and its steep-sided gorges—to the rolling country of Bowland and the Craven Lowlands provides one of the best geographical contrasts in the North of England.
To the geologist there are many interesting problems, in which considerable progress has been made in the last quarter of a century, but many points in which are still obscure. Some of these are: the change in the type of stratification from the Pendleside type and Bowland type at the southern end of the region through the Yoredale type to the Bernician of the north, and the satisfactory correlation of the different facies; the relation of the now famous ‘knoll’ lime- stones, best seen immediately south of the Craven Fault, to the Lower and Upper Carboniferous Limestones of more normal type, and the whole problem of knoll-structure ; the sharp folding immediately in front of the faults. Dr. Marr has pointed out the knoll-like structure produced in the Keisley Limestone of the Cross Fell inlier, and has compared it with the limestone of Draughton Quarry to the south of the Craven Fault. There are many folded greyish-white limestones in the knolls of Craven which are very much like those of Keisley ; the Carboniferous Limestone floor and the different times of its sub- mergence, on which new light has been thrown by Professor Garwood’s recent work. An interesting paper on this subject was presented by Dr. Vaughan last year—his last paper; the relation of the pre-Pennines—a part of the old Caledonian system, the rocks of which seem to have had cleavage developed in them during the early Devonian folding, and which suffered denudation in later Devonian and early Carboniferous times; the immense thickening of the Millstone Grit to the south, and the precise relation of its rock- material to the denudation of the Caledonian Alps; and the age of the various foldings and faultings which have determined (in the main) the present Pennines.
All these problems have their geographical aspect. The old Paleozoic floor in Ribblesdale and the bit of wild scenery of another type—an inlier in the Carboniferous of the Penygent plateau; the striking rounded and ovoid form of the Craven knolls; the apparently great thickness of grit of the Bowland Fells, and especially of the Pendle Range —these and many similar phenomena interest alike the geologist and the student of physical geography.
The age of the faults and folds has been discussed by several distinguished workers. There was, of course, the pre-Pennine folding in Devonian times; faulting was possibly in progress in Carboniferous times as taught by Mr. Tiddeman; great earth- movements occurred at the end of the Carboniferous period ; Professor Kendall has shown that there was upward movement of the Pennines in early Permian times, between the deposition of the Lower Brockram and the Upper Brockram ; the great faults, especially the Penniné and Craven Faults, and the earlier folding were probably Permo-Triassic and possibly in part post-Triassic (the Craven Fault is, in the main, later than the Dent Fault, as it cuts the latter sharply at the southern end near Kirkby Lonsdale); the great continent- and mountain-building movements of mid-Tertiary time probably gave (according to Dr. Marr) the final broad form to the
550 Notices of Memoirs—Professor W. S. Boulton—
Northern Pennines, and determined the general consequent drainage system of the region.
Dr. Marr, Professor Kendall, Professor Fearnsides, and others have dealt with some of the interesting and important Glacial and post- Glacial changes of drainage, of which there are many examples in the Northern Pennines. ‘These Pleistocene changes may be studied especially well in the Howgill Fells, the Bowland Fells, and the Craven Lowland country.
NOTICES OF MEMOTRS. —~>——_
I.—ApprEss ro THE GrotoeicaL Section oF THE BririsH AssociaTION FOR THE ADVANCEMENT oF Screncr, Nuwcasrie-on-Tynez, 1916.1 By Professor W. 8. Bourton, D.Sc., F.G.S., President of the Section.
E are assembled here in Newcastle-on-Tyne, the heart of a great industrial community, where coal, the very lifeblood of industry, has been raised for more than three centuries in ever- increasing amount; and of all minerals which our science has helped us to win from the earth for man’s comfort and use, coal must assuredly take pride of place. . .
It has been the custom for the President of this Section to deal with some large, outstanding question of theoretic interest, and on this occasion I wish to refer to the present outlook of Economic Geology, more especially in this country.
If we attempt to compare the growth of applied geology in Britain with that, say, in the United States of America, or even in our great self-governing Dominions, or to appraise the knowledge of, and | respect for, the facts and principles of geology as directly applicable to industry in these countries and in our own, or to compare the respective literatures on the subject, I think we shall have to confess that we have lagged far behind the position we ought by right of tradition and opportunities now to occupy. . The vast natural resources of the countries I have named have doubtless stimulated a corresponding effort in their profitable development. But making due allowance for the fact that Britain is industrially mature as compared with these youthful communities, we cannot doubt that in this special branch of geology, however splendid our advances in others, we have been outstripped by our kinsmen abroad.
This comparative failure to apply effectively the resources of geology to practical affairs is unquestionably due, in no small measure, to our ignorance and neglect of, and consequent indifference to, science in general, more “especially on the part of our governing classes. This War, with all its material waste and mental anguish, may bring at least some compensation if it finally rouses us from complacence and teaches us to utilize more fully the highly trained and specialized intelligence of the nation.
? Slightly abridged.
Our Coalfields: Present and Future Prospects. 551
The Geological Survey.
In any discussion of the present outlook of economic geology in Britain we naturally turn first to the work of the Geological Survey. When in 1835 the National Survey was founded with De la Beche as its first Director, it was clearly realized by the promoters that its great function was to develop the mineral resources of the Kingdom, which involved the systematic mapping of the rocks, and the collection, classification, and study of the minerals, rocks, and fossils illustrative of British Geology. For upwards of eighty years this work, launched by the enthusiasm and far-sighted genius of De la Beche, has been nobly sustained. We geologists outside the Survey are ever willing to testify to the excellence, within the Treasury- _ prescribed limits, of the published maps and memoirs. Indeed, it would be difficult to name a Government service in which the officers as a body are more efficient or more enthusiastic in their work. .. .
But the time is opportune, I think, when we may ask whether the Survey is fulfilling all the functions that should be expected of it; whether it is adequately supported and financed by the Government ; whether it should not be encouraged to develop along lines which, hitherto, from sheer poverty of official support, have been found impracticable.
It will be admitted that the re-mapping of the coalfields, which were originally surveyed on the old 1in. Ordnance Maps more than half a century ago, before much of the mining information now available could be utilized, is a primary duty and a pressing public necessity. But it would be a great mistake to allow other areas which have apparently little or no mineral wealth, and are destitute, so far as we at present know, of any geological problem of outstanding interest, like the problem of the Highland Schists, to remain, as at present, practically unsurveyed. Take, for example, the great spread of Old Red Sandstone in South Wales and the Border counties of England, which on the present Government maps is indicated with a single wash of colour, and here and there an outcrop of cornstone. It is true that the southern fringe of this area has been recently surveyed in more detail in re-mapping the South Wales Coalfield ; but there remain upwards of 2,000 square miles of Old Red Sandstone unsurveyed. A map indicating merely the outcrop of the main bands of sandstone, conglomerate, marl, and limestone would be of great assistance to engineers in such works as water-supply and sewage, as well as to agriculture. I am aware that many other areas more clamorously demanding a survey could be cited; but I give this example because it happens that a few months ago the Survey maps of the area were found to be useless for the purposes of an engineering work which had necessarily to be based upon the local geology.
It is sometimes said, and with truth, that the great function of a Survey is to produce a geological map which should be a ‘ graphic inventory’, so far as its scale permits, of the mineral resources, actual and potential, of a country. After all, such a map, even when accompanied with its horizontal section and used by the trained geologist, is a very imperfect instrument by which to summarize and
552 Notices of Memoirs—Professor W. S. Boulton—
accurately to interpret the results of the surveyor’s work. There is so much to express that a single map will not always suffice. It may be desirable to show not only the outcrops of the strata at the present surface, but the thickness of the beds, and even the shape of a buried landscape or sea-planed surface, now unconformably overlaid by newer rocks. That the Geological Survey are alive to the importance of such work is shown by some of their recent publications. The memoir on the Thicknesses of Strata i the Counties of England and Wales, excluswe of rocks older than the Permian, published this year, is a most valuable compilation, bringing together officially for the first time a vast amount of useful fact, mainly from open sections and borings. May we not look forward to the time when the Survey can issue maps with ‘isodiametric lines’ showing the thicknesses in the case of important beds; for example, sheets of productive coal-measures, water-bearing beds, and so forth? In any case, we may confidently expect maps that will show by contours the shape and depth of those buried rock-surfaces, whether unconformities or otherwise, which limit strata of peculiar economic value. The Director of the Survey has already given usa foretaste in his valuable and suggestive maps of the Paleozoic platform of South-East England,’ and in the contoured maps of the base of the Keuper and of the Permian to the east of the Yorkshire, Nottingham, and Derby Coalfield, and the rock-surface below sea-level in Lincolnshire.’
Some of the new edition 1 in. colour-printed maps, excellent though they are, suffer by being overburdened with detail already, and we ought to consider whether it is not possible to issue maps of selected districts in series, as is done in the beautifully printed atlases of the United States Geological Survey, where each map of the series shows one particular set of features. .. .
We have yet to realize that technical knowledge, of the highest. value to the country and obtained at great cost and labour, should be distributed as widely as possible, and at the lowest or even at a nominal charge. I would go further, and put much of the technical information in a simple and attractive form. We might even hope, for example, to eradicate the lingering superstition of the water divining-rod, which is still requisitioned by some public bodies. How admirably clear, simple, and direct is the information on water- supply in the little Survey memoir entitled Votes on Sources of Temporary Water Supply in the South of England and Neighbouring Part of the Continent, price 2d., evidently produced under the stress of War conditions, and all the better for it.
During the last few months a series of much more important publications by the Geological Survey has appeared. I refer to the Special Reports on the Mineral Resources of Great Britain, of which some six volumes are completed. The Survey is to be congratulated upon starting a line of investigation and report which is a return to some of its oldest and best traditions. The Preface, by the Director, to the first volume of the series, that on the Tungsten and Manganese Ores, is illuminating and symptomatic, for it reveals a consciousness
1 A. Strahan, Pres. Address to Geol. Soc., 1913. 2 Mem. Geol. Sury., Thicknesses of Strata, pp. 88 and 110.
Our Coalfields: Present and Futwre Prospects. 553
of our shortcomings in the past and points the way to reform in the future.
He says: “The effects of the War, in increasing the demand for certain minerals of economic value, have led to many inquiries as to the resources in Britain of some materials for the supply of which dependence has been placed upon imports, and have raised the question whether further exploitation and improvements in method of preparation of those minerals would now be justified.” :
Valuable mineral deposits in‘old workings, the delimitation of still unworked ground, old waste-products now of great value under changed conditions of demand, are vital matters dealt with in these volumes. In a pregnant passage the Director says: ‘‘It has become apparent also that some of our home products would be at least equal to material we have been importing, provided that they could receive equally careful preparation for the market, and that with improved treatment and greater facilities for transport, they would be fit to compete with some of the foreign materials.”
In the volume on Barytes and Witherite, it is stated that ‘ apart from the very highest qualities, there is no scarcity of barytes in Great Britain, but that notwithstanding that fact more than half the amount used in this country has been imported, and that 34 per cent of the amount used came from Germany”. Owing to fineness of grinding and low freights, the imports of this mineral from Germany have increased at a bigger rate than our own output,. a state of things that surely will never recur. .. .
The Geological Survey and the Imperial Institute.
I desire here to refer to the Research Department of the Imperial Institute at South Kensington. From the Scientific and Technical Research Department reports and papers appear from time to time on the mineral resources of Britain and the Colonies. Thus, ‘‘ The Occurrence and Utilization of Tungsten Ores” appeared in 1909, and similar reports on the ores of chromium, titanium, zinc, etc., and on the coal and iron resources of the British Crown Colonies and Protectorates have been published. These reports are all unsigned, although presumably written by competent persons. Such investigations, although primarily dealing with the Colonies, necessarily overlap to some extent similar work undertaken by the Geological Survey in this country. The point, however, I wish to make is that the work, both for Britain and the Crown Colonies and Protectorates in so far as it relates to prospecting, mapping, and reporting on mineral resources, could be done more effectively by the staff of the Geological Survey. There is no need to duplicate such a staff in the-Government service. Men of the standing of our Government surveyors, speciaily trained on the economic side, who are at present investigating our home mineral resources, are admirably fitted to do similar work in the Crown Colonies. As for the self-governing Dominions and India, they have their own Geological Surveys and may be relied upon to develop their own mineral wealth. .. .
554 Notices of Memoirs—Professor W. S. Boulton—
So far as I am aware, there is not any official connexion between the Imperial Institute and the Geological Survey; and it is to be regretted that in the recent Act of Parliament whereby the manage- ment of the Institute is definitely transferred to the Colonial Office, and which provides for the appointment of an Executive Council of twenty-two members to supersede the present Advisory Committee, no provision is made for the co-operation of the Geological Survey in the geological and mineralogical side of the Institute’s work. And may I say, in passing, that I think it is also a grievous mistake to develop a Research Department at the Institute without making some attempt to collaborate with the neighbouring Imperial College of Science and Technology, which, with its fine equipment and expert staff of researchers and teachers, should constitute a real Imperial College of Science and Research, in fact as in name?
But, these matters apart, it will be recognized on all hands that an ample field remains open for the energy and enterprise of the Imperial Institute as a Clearing House of scientific and technological know- ledge for the whole Empire, and especially for bringing the results of scientific investigation into touch with the main streams of industry and commerce. ...
The Development of Concealed Coalfields.
I pass on to consider what is, or should be, another phase of the work of our National Survey, namely, the discovery and development of concealed coalfields.
The Royal Coal Commissions of 1866 and 1901, and frequent addresses and reports by leading geologists in recent years upon the extension of our coalfields under newer rocks, bear witness to the sovereign importance of this branch of economic geology. One after the other the coalfields are being re-mapped by the Geological Survey, and we confidently expect the work to continue. But asthe known coalfields become opened up and gradually exhausted, the question of the survey and development of concealed coalfields becomes ever more pressing and vital to our position asa great industrial nation.
In the Yorkshire, Nottingham, and Derby Coalfield the rapid extension of workings eastward under the Permian and Triassic cover during recent years has been remarkable; and although the estimates of its buried Coal-measures adopted by the Commission of 1901, at that time thought conservative, have since come to be regarded as too liberal, we may still rely upon a buried field of workable coals larger in area than the exposed Coal-measure ground of this great coalfield, so that the whole combined field will prove the richest in our islands.
The Kent Coalfield has made a peculiar appeal to popular imagin- ation, partly because of its proximity to London, and its distance, amid England’s fairest garden, from the great and grimy industrial areas of the North. A recent address by Dr. Strahan vividly describes the rapid exploitation of this field.'
* ““The Search for New Coalfields in England’’: Royal Institution of Great Britain, March 17, 1916. Ee te)
Our Coalfields: Present and Futwre Prospects. 555
A problem of perhaps wider geological interest than that of the Kent Coalfield, and certainly of greater complexity, and containing the possibility of an even richer economic harvest, is the occurrence of buried Coal-measures under the great sheet of red rocks between the Midland coalfields, and under newer beds in the area to the south and east of them, towards London.
For the ultimate solution of this problem an appeal will have to be made to many geological principles of which the high theoretical interest is universally acknowledged, although their practical impor- tance is not so immediately apparent. Thus the minute zonal work in the Chalk, the laborious studies among Jurassic Ammonites, as well as the detailed investigations of minor transgressions and non- sequences in the Mesozoic rocks generally, will all have their value when estimating the nature and thickness of cover over the buried Coal-measures. . . .
One obvious line of attack is the more intensive study of the structure of the exposed coalfields, wlich is made possible by our ever-widening knowledge obtained largely from coal workings, present and past. . .
Geological Features of the Visible Coalfields which bear upon the Distri- bution and Structure of Concealed Coalfields in the South Midlands of England.
In touching upon this question of possible buried coalfields in the South Midlands of England, I wish briefly to refer to a few points connected with our detailed knowledge of already explored coalfields which must be taken into account. They may be grouped under two heads—
(1) The stratigraphical breaks which are said to exist within the Coal-measures themselves; and
(2) The post-Carboniferous and pre-Permian folding, and its relation to pre-Coal-measure movements.
Geologists who have made a close study of the detailed sequence of any British coalfield are fairly agreed that, while sedimentation was accompanied by a general subsidence, the downward movement was discontinuous, possibly oscillatory, as evidenced, on the one hand, by the occurrence of marine bands in a general estuarine series, and, on the other hand, by those coal-seams, particularly, which consist of terrestrial accumulations of plant-material. But on a critical analysis of prevalent views we meet with considerable difference of opinion as to the inferences to be drawn from the known facts.
Jukes-Browne, referring to Coal-measure time, says ‘‘ that it was a period of internal quiescence, a period in which terrestrial dis- turbances were at a minimum”’,’ and this notwithstanding his advocacy of the tremendous plication of the Malvern and Abberley Hills in the middle of the Coal-measure period, that is, in the interval between the Middle and Upper Coal-measures of England. Another high authority says ‘‘The Coal-measure Period as a whole was one of crust movement ’’.?
1 The Building of the British Isles, p. 169, 1911. 2 Q.J.G.S., vol. lvii, p. 94, 1901.
556 Notices of Memoirs—Professor W. 8. Boulton—
Dr. Gibson, after a detailed survey of the North Staffordshire Coalfield, where the Middle and Upper Coal-measures are fully and typically developed, asserts that ‘‘no break has been detected in the Coal-measure sequence’’;! and a like conclusion is to be drawn from the work of the Government surveyors and from borings in the Yorkshire, Derby, and Nottingham Coalfield and that of East Warwickshire.
Mr. Henry Kay *? would fix a local unconformity at the base of the Halesowen Sandstone of South Staffordshire, and another at the base of the Keele Beds (or so-called Lower Permian Marls); while in the Coalbrookdale Coalfield the well-known Symon Fault, described by Marcus Scott as a great erosion-channel in the Middle or Productive- measures, subsequently filled up by the unproductive Upper Coal- measures,*® was interpreted by W.J. Clarke in 1901 * as a pronounced unconformity, a view which has been generally accepted ever since, and which was eagerly seized upon by those who hold that the Malvernian disturbance occurred at this time.
The plate which illustrates Marcus Scott’s paper on the Symon Fault *° shows the upper beds plotted out from the lowest workable seam in the older measures, which he assumes to be horizontal (their original position); while Clarke, using Scott’s data, plots his sections from the base of the Upper-measures, which he uses as a horizontal datum-line.* Incidentally I may remark that in both cases the sections are drawn with a much-exaggerated vertical scale, and, of course, correspondingly exaggerated dips.
In my opinion, both these interpretations are misleading (apart from the question of seale), because in neither case is the adoption of the horizotal datum-line strictly justified by the facts. In the one case the curvature of the basin is made too great, and in the other the dips in the Middle-measures are unduly increased ; for, as mining plans show, the base of the Upper-measures is by no means horizontal. The fact is that the undulations in the measures throughout the _ coalfield are extremely slight, there being scarcely any perceptible dip in the strata, as noted by Scott, except near what is called the ‘* Limestone Fault’’, where the dips, as will presently appear, can be otherwise accounted for. Furthermore, there is a significant absence of faults other than those which affect Middle and Upper- measures equally.
I believe there is another and a simpler explanation of this classic disturbance, and one which harmonizes, in part, the views of both Scott and Clarke; and at the same time helps to give us a reasonable interpretation of the apparently conflicting statements which have been made by working geologists respecting the relationship of the Coal-measure divisions in the Midlands.
The Keuper Marls of the Midlands occur either in horizontal or
1 Q.J.G.S., vol. lvii, p. 264, 1901. 2'Q.J.G.8., vol. Ixix, pp. 433-53, 1913. 3 Q.J.G.S., vol. xvii, pp. 457-67, 1861. 4 Q.J.G.S., vol. lvii, pp. 86-95, 1901.
> Thid.
8 Tbid.
Our Coalfields: Present and Future Prospects. 5517
very gently undulating sheets, but Dr. Bosworth has shown that around Charnwood Forest they dip in all directions, ‘‘ sometimes to the extent of 20 or. even 30 degrees,” and that everywhere the inclination is in the direction of the rock-slope beneath, though always at a smaller angle than the slope. This local dip (or ‘tip’, as he calls it) ‘‘seems most likely to have been largely caused by contraction of the marls under pressure and by loss of moisture ’’.!
In a paper dealing with the Coal-measures of the Sheffield district published this year,? Professor Fearnsides directs attention to a research by Sorby, embodied in a memorable contribution to the Geological Society of London in 1908? upon the contraction of clay sediment due to loss of water. It appears to me that the penetrating genius of Sorby, with that clarity of vision which comes from patient and exact quantitative experiment, may help us to clear up some of the difficulties to which I have referred. If the Coal-measure clays have lost something like five-sixths of the original thickness they possessed as mud or~ slime, as Sorby’s quantitative experiments seem to indicate, is it not possible that the discordance we are discussing between the Middle and Upper Coal-measures is due, in part at all events, to differential contraction and consequent local sageing during the extremely slow squeezing out of the water by the pressure of overlying sediment? We must remember that the Middle Coal-measures consist essentially of clays, and that over a large part of the Midlands they were deposited on a very uneven floor, and that to start with they were therefore of very variable thickness. It is easy to see, also, that an arenaceous fringe of sediment where the measures abut against a rise in the floor would suffer far less vertical contraction from this cause than the clay, because of the very diminished ‘‘ surface energy’’ of the constituent sand particles, and that this would have the effect of accentuating the dip due to the sag.
It is to be noted that Scott's observations and the bulk of his section referred to the central parts of the coalfield, while Clarke deals primarily with the district just north of Madeley and along the south-eastern fringe of the ‘‘ Limestone Fault’, which may prove to be, in my opinion, in its early stage at all events, a pre- Coal-measure ridge of limestone.
It is quite possible, indeed probable, that portions of the undulating surface of the Middle Coal-measures suffered local erosion, which, however, need not imply folding of the beds with prolonged subaerial denudation; for it seems likely that such local erosion was sub- aqueous, producing a non-sequence similar in character (and origin perhaps) to the relatively small stratigraphical breaks which have been recognized recently in the Jurassic strata in the West of England and elsewhere.
Thus, in North Staffordshire, where the Midland Coal Basin is deepest, no break between the Upper and Middle-measures exists ; but approaching the southern margin of the basin, to the south of
1 The Keuper Marls around Charnwood, pp. 47-50, 1904-11.
2 Trans. Inst. Min. Eng., vol. 1, pt. iii, 1916. > Q.J.G.S., vol. lxiv, pp. 171 et seq., 1908.
558 Notices of Memoirs—Professor W. S. Boulton—
the South Staffordshire Coalfield, where the Middle Coal-measures are rapidly thinning, there are, if Mr. Kay’s observations are correct, signs of a non-sequence or local unconformity. The same is true, but on a larger scale, in the Symon Fault of the Coalbrookdale Coal- field,’ and is to be explained, if the above reasons are valid, by the rapid variation in thickness of the Middle-measures, due to the irregular floor upon which they rest, to the consequent sagging of the beds, and also to local subaqueous erosion. Further, such partial unconformities or non-sequences would generally indicate the proximity of that marginal fringe where the Upper-measures overlap the Middle and rest on pre-Coal-measure strata.
The Middle and Upper Coal-measures of the Midlands record general but intermittent subsidence, with a considerable pause at the end of Middle Coal-measure time, followed by a much more general depression, as shown by the extended and overlapping sheet of Upper Coal-measures. But there is no evidence which I regard as convincing that regional elevation or great orogenic movements occurred until after the Upper Coal-measures were laid down.
The floor upon which the Middle Coal-measures were deposited along the southern fringe of the Midland Coalfields was a sinking and already folded and denuded floor, and it is to be expected, there- fore, that these measures rest in submerged gulfs and estuaries, which would mean that some, at any rate, of the several coal basins were originally isolated wholly or in part, and their separation is not to be interpreted as due to folding and subsequent denudation.
Dr. Newell Arber has argued that the Middle Coal-measures of Coalbrookdale, the Forest of Wyre, and the Clee Hills, were deposited in three separate basins, which as regards the Sweet Coal or Pro- ductive-measures were never continuous.” On the other hand, just as it is certain that the Productive-measures on either side of the South Pennines were originally continuous, so it is probable that as we go northward from this southern fringe the Productive-measures spread out into more extensive sheets... .
As an example of such intensive geological work, I should like to refer to the detailed plotting by Mr. Wickham King of the Thick Coal of South Staffordshire on the 6in. maps. For more than twenty years he has been engaged in collecting and tabulating an immense number of levels and other data from colliery officials, and from old and sometimes half-forgotten borings; and he has now produced a contoured map and a model to the same scale, showing in great detail the folds and faults in the Thick Coal. In 1894 Professor Lapworth, to whose initiative this work was due, emphasized the value of such ‘‘plexographic maps” of coal seams, and predicted that such maps would be drawn in all the coalfields.* The data obtained in South Staffordshire also enable us to determine, at
1 Mr. Wedd has recently described a similar break between the Middle and Upper Coal-measures of the northern part of the Flint Coalfield. (See Summary of Progress of Geol. Surv. for 1912, pp. 14, 15.)
? Phil. Trans. Roy. Soc. London, Series B, vol. eciv, pp. 431-7: “‘ On the Fossil Floras of the Wyre Forest, etc.”’
3 Fed. Inst. Min. Eng., vol. viii, p. 357, 1894-5.
Our Coalfields: Present and Future Prospects. 559
some places exactly, at others approximately, the shape of the pre- Coal-measure floor and the outcrops of its constituent formations; and to disentangle, in part, the pre- and post-Coal-measure move- ments. Thus we get additional evidence to show that before Middle Coal-measure time, denuded folds, with a north-west or Charnian trend, and other folds with a north-east or Caledonian trend prevailed. The post-Carboniferous and pre-Permian movements emphasized and enlarged some of these folds. As already remarked, a matter of great practical importance is as to how far these pre- Coal-measure folds interfered with the continuity of deposition of the productive series, with, for example, the original extension of the Thick Coal of South Staffordshire. Since Jukes-Browne’s time it has been known that the Thick Coal group as a whole thins, and the coal itself deteriorates, southward towards the Clent and Lickey Hills. It is the discontinuity and local deterioration in an easé and west direction, beyond the Boundary Faults, due to pre-Coal-measure flexures, and irrespective of post-Carboniferous movement, that I have been emphasizing.
The powerful disturbances of post-Carboniferous and pre-Permian age, which have affected all our coalfields, I have no intention of discussing here. Professor Stainier, the Belgian geologist, has just published a lengthy and able discussion on the subject,’ while the lucid account by Dr. Strahan in his Presidential Address in 1904 and his recently snmmarized views in a lecture to the Royal Institution will be in the minds of all geologists.
I do not think, however, that it is generally realized what a great part the two dominant pre-Carboniferous systems of folding played in determining the trend of the post-Carboniferous flexures. In the South Pennines, in the Apedale disturbance of North Staffordshire and in the Malverns we have nearly north and south folds due to a great easterly thrust; but elsewhere in the Midlands and the North the movements were taken up, to the west of these north and south lines by the Caledonian folds, and to the east by the Charnian flexures. It is very instructive to watch in the centre of the South Staffordshire Coalfield the old Charnian fold of Silurian rocks that make up Dudley Castle Hill, the Wren’s Nest, and Sedgley Hill struggling, as it were, against the newer post-Carboniferous easterly squeeze, which has impressed a north and south strike upon each of the domes, arranging them en échelon from north-west to south-east, and incidentally permitting the great laccolitic intrusion of Rowley Regis.
Tt will be found, however, that the vast majority of the folds and faults in the Midland and Northern Coalfields are not along what may be called strict Hercynian lines—that is, north to south and east to west—but along the locally older Caledonian and Charnian directions. It was as if the great north and south flexures of the Southern Pennines and Malverns, and the east and west Armorican folds of the South of England, to a large extent exhausted the mighty attack of the Hercynian movements coming from the South and Kast of Europe;
1 Trans. Inst. Min. Eng., vol. li, pt. i, pp. 99-153, 1916.
560 Notices of Memoirs—Professor W. S. Boulton—
while smaller intervening and relatively sheltered areas were allowed to yield along their old north-west and north-east lines.
Need for Systematic Survey by Deep Borings.
After all, when we turn our attention to the possible extension of the Coal-measures under the newer strata of South-Central England, the geological data at our disposal are lamentably and surprisingly few. Notwithstanding our eagerness to unravel the difficulties, and so to open up new fields for mining activity, very little positive progress has been made in the last twenty years. Of late a few deep borings have been sunk; one near High Wycombe, after piercing the Mesozoic cover, ended in Ludlow rocks; another at Batsford, in Gloucestershire, fifteen miles north of the well-known Burford boring, struck what are regarded as Upper Coal-measures, also resting on Silurian rocks.
At the present time it seems specially fitting to call attention once again to our haphazard method of grappling with this great economic question. Are we to go on indefinitely pursuing what is almost ‘wild-cat’ boring, to use the petroleum miner’s expressive slang? Or shall we boldly face the fact that systematic exploration is demanded; and that this pioneer work is a national obligation, the expense of which should be a national charge ?
At the meeting of the Organizing Committee of Section C, already referred to, a recommendation was forwarded to the Council in the following terms :—
‘‘The Council of the British Association for the Advancement of Science recommends that the site, depth, and diameter of every ‘borehole in the British Isles, exceeding 500 feet in depth, be compulsorily notified and registered in a Government Office. That all such boreholes be open to Government inspection during their progress. That copies of thé journals and other information relating to the strata penetrated by the boring be filed ina Government Office under the same restrictions as those relating to plans of abandoned mines.”’
I would go further and urge that the Government should under- take the sinking of deep borings at selected points. This is no new idea. In his Presidential Address to the Geological Society of London in 1912 Professor Watts pleaded most forcibly the vital importance of a State-aided underground survey of the area to which I have referred. The work is too vast for individual effort, or even for a private company to undertake. It is not suggested that deep borings should be sunk with the express purpose of finding coal. What is wanted is a systematic survey by borings at such spots as are likely to throw light upon the structural framework of the Paleozoic floor and the thickness of its cover... .
For many years I lived near our great exporting centres of the finest steam coal in the world; and as I watched the steady and incessant streams of coal-wagons, year in, year out, coming down from the hills, I was constantly reminded that we are rapidly draining the country of its industrial life-blood. Is it an extravagant demand to ask that an infinitesimal fraction of this irreplaceable Nature-made
Petroleum: Present and Future Prospects. 561
wealth should be set aside to provide the means for the discovery and development in our Islands of new mineral fields ?
Chemical and Microscopical Investigation of Coal-seams.
. The recovery of bye-products in the coking of coal, which up to
the beginning of the War was almost exclusively undertaken by the Germans, is likely in the future to become an important British | industry. This will ultimately demand a thorough knowledge of the microscopic and chemical str ucture of all the important coking seams in our coalfields.
Remembering how varied both in microscopical structure ae chemical composition the individual laminz of many of the thick coal-seams are, it will readily appear how important such a detailed investigation may become, having regard to the great variety of these bye-products and their industrial application. Moreover, thin seams, hitherto discarded, may pay to be worked, as may also an enormous amount of small coal, estimated at from 10 to 20 per cent of the total output, which up to the present has been wasted.
Geology of Petroleum.
It has been frequently remarked that in order to account for the vast accumulation of coal in the Carboniferous strata, it is necessary to postulate a special coincidence over great areas of the Northern Hemisphere of favourable conditions of plant growth, climate, sedimentation, and crustal subsidence; conditions which, although they obtained at other geological periods over relatively small areas, were never repeated on so vast a scale. Having regard to the estimates of coal deposits in Cretaceous and Tertiary strata, published in our first International Coal Census, the ‘‘ Report on the Coal Resources of the World’’,! it would appear that we might reasonably link the Cretaceo-Tertiary Period with the Carboniferous in respect of these peculiar and widely prevalent coal-making conditions. For I find that of the actual and probable reserves of coal in the world, according to our present state of knowledge, about 43 million million tons of bituminous and anthracite coal ‘exist, the vast bulk of which is of Carboniferous age; while there are about 3 million million tons of lignites and sub-bituminous coals, mostly of Cretaceous
and Tertiary age.
When we look to the geological distribution of petroleum, we note that it is to be found in rocks of practically every age in more or less quantity, but that it occurs par excellence, and on a great commercial scale, in rocks of two geological periods (to a smaller extent in a third); and it is significant that these two periods are the great coal-making periods in geological history—the Carboniferous and the Cretaceo- Tertiary. .
‘The world’s production of petroleum has trebled itself within the last fifteen years. In 1914 the United States of America produced 66°36 per cent, and North and South America together nearly three- fourths of the world’s total yield; while the British Empire
1 Report on ‘‘ The Coal Resources of the World’’, for the Twelfth Intern. Geol. Congress, 1913.
DECADE VI.—VOL. IlI.—NO. XII. 36
562 Notices of Memoirs—Professor W. S. Boulton—
(including Egypt) produced only a little more than 2 per cent. In the near future Canada is likely to take its place as a great oil- and gas-producing country, for large areas in the middle-west show promising indications of a greatly increased yield. But Mexico is undoubtedly the country of greatest potential output. Its Cretaceous and Tertiary strata along the Gulf Coastal Plain are so rich that it has been stated recently on high authority that ‘‘ a dozen wells in Mexico, if opened to their full capacity, could almost double the daily output of the world’’.
As is well known, natural supplies of petroleum are not found in the British Isles on a commercial scale; but for many years oil and other valuable products have been obtained from the destructive distillation of the oil shales of the Lothians. If Mr. Cunningham Craig is right in his views recently expressed,* these shales, or rather, their associated freestones, have been nearer to being true petroliferous rocks than we thought; for he believes that the small yellow bodies, the so-called ‘spores’ in the kerogen shales, are really. small masses of inspissated petroleum absorbed from the porous. — and once petroliferous sandstones with which the shales are interstratified.
If recent experiments on peat fulfil the promise they undoubtedly show, we shall have to take careful stock of the peat-bogs in these Islands. It is well known that peat fuel has been manufactured in Europe for many years. But my attention has been called to a process for the extraction of fuel-oil from peat, which has been tried experimentally in London, and is now about to be launched on a commercial scale, utilizing our own peat deposits, like those of Lanarkshire and Yorkshire... .
It is sometimes asked whether the adoption of mineral oil as a power-producer is likely to supplant coal, and thereby seriously reduce the output of that mineral. The world’s yield of petroleum will doubtless go on increasing at a very great rate; but from the experience gained in some of the fields in the United States and Eastern Canada, it seems unlikely that this increase can continue for a very long period. Practically complete exhaustion of the world’s supply is to be looked for within 100 years, says one authority.2 Even if the output rose to ten times the present yield, it would represent only about half the present world output of coal, and it is practically certain that so high a yield of oil could not be maintained for many years. Owing to the almost certain rapid increase in the output of coal, estimates made by the same authority already quoted indicate that the total production of petroleum could never reduce the world’s output of coal by more than about 64 per cent.*
For us, and probably for those of the next generation, the geology
1 Ralph Arnold, ‘‘Conservation of the Oil and Gas Resources of the Americas’’: Econ. Geol., vol. xi, No. 3, p. 222, 1916.
2 Institution of Petroleum Technologists, April, 1916.
3 H. S. Jevons, British Coal Trade, 1915, p. 710.
+ Thid., p. 716.
Underground Water. 563
of petroleum will continue to be of immense practical importance ; but coal will doubtless remain our great ultimate source of power.
An obligation rests upon us to see that the oil resources of the British Empire and of territories within our influence are explored, if possible, by British geologists, with all the specialized knowledge that can be brought to bear; and I am glad to think that the University of Birmingham and the Imperial College of Science and Technology, London, with this end in view, are doing pioneer work in giving a systematic and specialized training to our young petroleum technologists. . ..
Underground Water.
Since the year 1856, when the Frenchman, Darcy, attempted by a mathematical formula to express the law governing the trans- mission of water through a porous medium, nearly all investigation upon this important engineering question has been carried on in the United States; and many of the results have been published in the valuable Water Supply and Irrigation Papers of the United States Geological Survey. Particular reference should be made to the work of Hazen, King, Darton, and Slichter, the last of whom has given us the clearest and most convincing explanation of the behaviour of water percolating through a porous rock. He and his co-workers have experimentally investigated the factors which determine the underground flow, and expressed their relationship by mathematical formule ; and they have made it clear, by careful measurement | extended over long periods, that the rate of flow through average porous water-bearing rocks and under ordinary pressure gradients is extremely small, something like a mile a year, or even less.!
Geologists who are in touch with the application of these principles to such engineering matters as water-supply, sewage, and drainage will readily appreciate the great value of such researches. At the same time, one must reluctantly confess that, with few exceptions, the investigations have not been adequately grasped and utilized in present-day engineering practice in this country. As to their geological bearing, we have only to be reminded of the important processes of solution, cementation, and fossilization in rocks in order to comprehend the value of a just estimate of the behaviour of this vast. and slow-moving chemical medium in which the superficial rocks of the crust are immersed. . . .
The conditions are so complex and the controlling factors vary so much in different river-basins that it is impossible to obtain for the whole country anything like an accurate and reliable expression for the relationship between rainfall, percolation, and run-off. The interminable and costly legal wrangles during the passage of a Water Bill through Parliament bear witness to the truth of this statement. What is needed is a continuous record in the different catchment areas of the country of observations on river discharge, percolation, and so forth, extended over many years. Fortunately, our rainfall observations, thanks to the British Rainfall Organization, are now
1 Slichter, Water Supply Paper No. 67, U.S. Geol. Surv.: ‘‘ The Motions of Underground Waters.’’
564 Notices of Memoirs—Edward A. Reeves—
or could be made, ample for this purpose. But except for attempts by local water companies and corporations to obtain the data I have referred to, there exists no public control to deal with the matter.
In 1906 a Committee of the Royal Geographical Society, with Dr. Strahan as Chairman, and with the aid of a grant from the Royal Society, undertook to investigate river discharge, suspended and dissolved matter, rainfall, area, and geological conditions in some specially selected river-basins, The final report, which has now appeared, dealing with the Severn above Worcester, the Exe, and the Medway, constitutes a most valuable record.
It will be obvious to all geologists that important fleanetiont questions, such as the rate of denudation and deposition, and vital engineering matters, such as the position and permanency of harbour works, would be greatly assisted by exact quantitative estimates of the material carried down by rivers.
In 1878 Joseph Lucas urged the importance of a Hydro- geological Survey of England, and “the Royal Commission on Canals and Waterways in their final report in 1909 recommended the appoint- ment of some public authority to do for the whole country what this Committee has so admirably done for these three river-basins.
Organization of Expert Knowledge.
We are reminded by the report of a later Royal Commission—that on Coast Erosion in 1911—that systematic observations and the collation and organization of geological and engineering knowledge are urgently needed in connexion with the protection of our coasts and the reclamation of new lands. For it will be remembered that the Commission found that during the last thirty-five years the gain of land, as shown by Ordnance Survey maps, has been more than seven times the loss by erosion.
Here, again, the British Association may reflect with pride that it paved the way for this national inquiry. For many years its Committee on Coast Erosion gathered and collated evidence on erosion, and induced the Admiralty to instruct the Coastguard to observe and report upon changes that take place from time to time. . . .
Is it not abundantly clear that in economic geology, as in the case of other applied sciences, we must rely in the future less upon chance individual effort and initiative? We must concentrate, centralize, and organize; and at every stage we shall need expert control and advice as regards those larger scientific issues of national importance which have a direct practical bearing.
II—Tue Maprine oF tHE Karru, Past, Presenr, anp Furure. Being an abridged report of Address to the Geographical Section (E), British Association, Newcastle. By Epwarp A. Renvzs, F.R.A.S., F.R.G.S., President.
FTER a brief allusion to the increasingly important part Science had been called upon to play in the present great crisis and the value of a more thorough and general scientific training, the President
The Mapping of the Earth. 565
pointed out the various ways the present War will affect the map- maker, owing to the surveying and arranging of new boundaries, etc , as after all is over our present maps and atlases will have to be very largely revised and brought up to date.
He divided his Address into the following headings : —
1. A brief general summary of what has been done in the past towards the mapping of the earth’s surface.
2. A sketch of how things stand at the present time.
3. A few remarks upon future work, specially as regards instruments and methods.
Commencing with a historical sketch of geographical exploration and representation of the surface features of the earth from as early a date as B.c. 276, the President stated that—
It was not until the latter part of the fifteenth century, the time of the great Portuguese and Spanish discoveries, that any real advance was made, but then Europe seemed to awake from a long sleep, and a grand new start was made.
One of the first acts of King John II of Portugal (1481-95), whose memory deserves to be equally held in respect with that of his great uncle Prince Henry, was the calling together of the Committee, or ‘Junta’, of learned men to consider the best means of finding the latitude when the Pole Star was too low to be of service, to decide upon the most approved form of instrument for the taking of observa- tions, and to furnish suitable tables of declination, etc., for the computations. Equipped with the new tables, which may, perhaps, be considered the first Nautical Almanac, and the simplified astrolabe, the Portuguese navigators started on the famous voyages, with a much better chance of properly fixing positions than their predecessors. The Vernier had not: yet been invented, and so the difficulty of obtaining accurate readings of the circles was still considerable. To overcome this difficulty it was decided to construct astrolabes with very large®circles, and the instrument carried by Vasco da Gama in his famous voyage round the Cape in 1497 had a circle which measured just over two feet, in diameter. . .
The difficulty of taking anything like accurate observations at sea was for centuries a very serious one, and long before the invention of the reflecting quadrant or sextant many were the attempts to devise some instrument for accomplishing this... .
It was not until the ingenious invention of the reflecting octant, suggested first of all by Sir Isaac Newton, that anything approaching accuracy was possible. Hadley’s quadrant was the first of such instruments to be put into actual use, but there is no doubt that the idea should be ascribed to the famous Sir Isaac Newton, although the instrument was probably independently invented by Hadley.
With the invention of the sextant, or its predecessors the octant and quadrant, rapid progress was made in improvements in navigation and surveying instruments.
The introduction of the Nonius by Peter Nunez in the middle of the sixteenth century, and later of the Vernier by the Frenchman Francis Vernier, which, owing to its simplicity, soon superseded the
566 Notices of Memoirs—Edward A. Reeves—
former, were of great importance, since it was no longer necessary to construct the enormous large arcs and circles which had hitherto been indispensable to give anything like accuracy.
The magnetic compass not only made an enormous difference in navigation and exploration by sea, since it enabled the sailor to launch boldly out into the unknown oceans with confidence, but it soon began to leave its mark on land-surveying and geographical exploration. Much has been written on the invention of the compass, and many have been the disputes upon the subject, but it was certainly in use in Mediterranean countries of Europe as early as the twelfth and thirteenth centuries. The date when it was first used for land-surveying is not known exactly, but in Europe it was probably about the early part of the sixteenth century... .
The surveying equipment of the pioneer explorer of early days, say, of from twenty to sixty years ago, usually consisted of a sextant and artificial horizon, a chronometer or watch, prismatic compass, boiling-point thermometers, and aneroid. With the sextant and artificial horizon the astronomical observations for latitude and longitude were taken, as well as those for finding the error of the compass. The route was plotted from the compass bearings and adjusted to the astronomically determined positions. The latitudes were usually from meridian altitudes of the sun or stars, and longitudes from the local mean time derived from altitudes east or west of the meridian, compared with the times shown by the chronometer, which was supposed to give Greenwich mean time.
The sextant, in the hands of a practical observer, is capable of giving results in latitude to within 10” or 20”, provided it is in adjustment, but the difficulty is that the observer has no proper means of testing for centering and graduation errors.
The great drawback to the sextant for survey work is that it is impossible to take accurate rounds of horizontal angles with it, since, unless the points are all on the same level, the angles must be too large. It is essentially a navigator’s instrument, and nowadays has been almost entirely superseded by the theodolite for land- surveying.
As regards the longitude, the difficulty was always to obtain a steady rate for the chronometer, owing principally to the unavoid- able oscillations and concussions met with in transit. Formerly it was customary to observe lunar distances for getting the Greenwich mean time instead of trusting to the chronometers, but these, even with the utmost care, are very unsatisfactory.
In more recent years the occultation of a star method of finding the Greenwich mean time superseded almost entirely the lunar distance, but all of these so-called ‘absolute’ methods of finding longitude are fast becoming out of date since the more general introduction of triangulation and wireless telegraphy.
Heights of land were usually obtained by the boiling-point thermometer or aneroid.
This, then, was the usual equipment of the pioneer. With such an outfit the greater part of the first mapping of Africa and other regions of the world was carried out, with results that were more or
The Mapping of the Earth. 567
less reliable according to the skill of the explorer and the time and opportunities at his disposal.
In recent years considerable improvement has been made in the instruments and methods of the geographical surveyor: the introduc- tion of the Invar tape for the measuring of the baselines, the more general application of triangulation, the substitution of the theodolite for the sextant, the use of the plane-table for filling in the topo- graphical details of the survey, the application of wireless telegraphy to the determination of longitudes, these and other improvements have all tended to greater accuracy and efficiency in geographical and topographical mapping, so that in many respects the rough approximate methods of the earlier explorers are fast being super- seded by instruments and methods more in keeping with modern requirements in map-making.
Still, the principle underlying all surveying is the same, and the whole subject really amounts to the best and most accurate methods of measurement with a view to representing on a plane, on a greatly reduced scale, the leading features of a certain area of the earth’s surface in their relatively correct positions; and so it resolves itself into geometrical problems of similar angles and _ proportional distances. This being the case, it is clear that it becomes in the main a question of correct angular and linear measurements, and all the improvements in survey methods have had for their object the increased accuracy of accomplishing this, together with greater facility for computing the results. . . .
So far what I have said has had chiefly to do with some of the earlier attempts at surveying and map-making, and the instruments and methods by which these have been carried out; and I will now try to give you an outline of what has been done in comparatively recent times, and state briefly the present position of various parts of the world as regards the condition of their mapping and the survey basis upon which their maps depend.
Little by little civilized man, by his daring, his love of adventure, and the necessities of events and circumstances, has penetrated into the unexplored parts of the earth and pushed back the clouds and mists that so long shrouded them from his knowledge, until at the present time the regions that are entirely unmapped are very few indeed, and do not amount to more than about one-seventh of the whole land-surface of the globe, including the unexplored areas of the Polar regions, which may be either land or water. Not content with a mere vague acquaintance, he has striven for greater accuracy, and has turned to various branches of science and called them to his aid, in order that he may obtain more correct knowledge and a better comprehension of the earth’s features. To enable him to fix with definiteness the position of places upon its surface, map out the various land-forms, and obtain their accurate measurements, he has consulted the astronomer and mathematician. Commencing, as we have seen, with the rudest instruments and measuring apparatus, these, as greater accuracy was required, have gradually been improved, until the present-day appliances and equipment of a surveyor are a wonder of refinement and delicacy.
568 Notices of Memoirs—Edward A. Reeves-—
I have attempted to form an estimate of the condition of the world’s surveys as represented by the differently tinted areas on the maps for 1860 and 1916;' and, taking the total area of the land- surface of the earth, together with the unknown parts of the Arctic and Antarctic regions which may be either land or water, to be 60,000,000 square miles, I have obtained the following results :—
1860 1916 Sq. Stat. Proportion Sq. Stat. Proportion Miles. to Whole. Miles. to Whole. 1. Mapped from accurate ed graphical surveys based on| 1,957,755=0°0326 8,897,238=0°1482 triangulation or rigorous | or roughly #5 or roughly + traverses 2. Mapped from less reliable lees bay surveys, chiefly non-topo- Ge ck on ait a as, ee. graphical rion: hae 3. Mapped from route traverses\ 25,024,360=0°4170 37,550,552—0°6258
and sketches ah or roughly 2 or little less than 2
4. Entirely unsurveyed and) 30,997,054=0-5166 8,350,794=0°1391 unmapped { J or just over 4 or little less than +
These proportions can perhaps be more clearly seen from the following small diagram.
1860 19 16
Diagram showing the relative proportions of the earth’s surface in 1860 and 1916, which are—1, fully mapped; 2, partially mapped ; 3, slightly mapped; and 4, not mapped in the two periods referred to. It is plain that with the same rate of progress as that of the past sixty years or so it would take just over four hundred years more ~ 1 The two maps have not been reproduced from Mr. Reeves’ Address, but
the small diagram is given and shows the areas mapped and unmapped and their relative proportions.
The Mapping of the Earth. 569
to complete the accurate trigonometrical surveying and topographical mapping of the earth’s land-surface, including the parts of the Polar regions that may possibly be land—that is, the 60,000,000 square miles which we have taken for this total area; but this will certainly not be the case, since the rate at which such surveys have been carried out has been greatly accelerated during recent years, owing to the rapidly increasing demands for accurate topographical maps, improvements in methods, and other causes, so that it will possibly not be half this time before all the parts of the earth’s surface that are likely to be of any use to man as settlements, or capable of his development, are properly surveyed and mapped. There are, of course, regions, such as those near the Poles and in the arid deserts, that are never likely to be accurately triangulated and mapped to any extent, and it would be mere waste of time and money to attempt anything of the kind... .
Many and varied have been the influences that have led to the surveying and mapping that have already been accomplished, and it would be interesting if we had time to analyse them. Among the preliminary surveys, I think it would be found that military operations would hold an important place. Many an unexplored region has been mapped for the first time as the result of frontier expeditions, such as those of the frontier regions of India and parts of Central and South Africa, while the need of a more exact acquaintance with the topographical features for military require- ments have frequently led to more exact trigonometrical surveys. Our own Ordnance Survey is indeed an example of this, for in the first place it resulted from the military operations in Scotland in the latter part of the eighteenth century.
Among other causes that have resulted in surveying and mapping might be mentioned the delimitation of boundaries, com- mercial or industrial undertakings, such as gold-mining and land- development, projects for new railways, all of which have at times been fruitful in good cartographical results. Nor must we forget Christian missions. The better-trained missionary has always recognized the importance of some sort of a survey of the remote field of his operations, and the route to it, if for no other reason, with a view to the good of his fellow-workers and those who come after him; and in the earlier days especially perhaps most of all pioneer mapping was done by the self-sacrificing service of the missionary. We have only to think of such men as Moffat, Living- stone, Arnot, Grenfell, and others of the same sort to be reminded of the debt due to the missionary from all interested in geographical mapping... .
The future surveyor will be in a much better position than his predecessors, not only on account of the improvements in instruments and apparatus for his work, but because, in many parts, a good beginning has been made with the triangulation to which the new surveys can be adjusted. In Asia a considerable amount of new work of this kind has been done over the frontier of India in recent years by the Survey of India, among the more important of which is the connecting of the Indian triangulation with that of Russia by way
570 Notvces of Memoirs—The Mapping of the Earth.
of the Pamirs. The many boundary surveys that have been carried out in Africa, the triangulations of Egypt, the Soudan, Kast and South Africa, and other parts of the continent are well advanced, and will be of the utmost value to the future surveyor. One of the most important lines is the great triangulation which, it is hoped, will some day run across the continent from south to north, from the Cape to Egypt. Owing to the energies of the late Sir David Gill, this important chain of triangles has already got as far as the southern end of Lake Tanganyika; the part to the west of Uganda near Ruwenzori has also been finished, and it now remains to carry the chain through German East Africa and down the Nile Valley. The latter, it is hoped, will by degrees be accomplished by the Soudan and Egyptian Survey Departments, although it may be delayed for some years yet; and the former, which was to have been undertaken by the Germans, it is hoped will after the War be accomplished by British surveyors, through—not German East Africa—but newly acquired British territory. Running right through parts of Africa that are but imperfectly mapped in many districts, the stations of this triangulation will be invaluable for the adjustment of any network of triangulation for future surveys in the interior, and, indeed, has already been utilized for the purpose.
The carefully carried out boundary surveys between various countries of South America will be of the greatest assistance in future explora- tion and survey in the interior of that continent, wherever they are available, while the Survey Departments of Canada and the United States are doing excellent work and extending their surveys far into the imperfectly mapped regions of North America. So, altogether, the surveyor of the future will soon have a good foundation of reliable points to work from. It is important to remember that running a chain of triangles across a country, though important as a framework, does not constitute a map of the country; and what is wanted, at any rate in the first place, is a series of good topographical maps, based upon triangulation, showing the leading features with sufficient accuracy for the purposes of ordinary mapping, so that on scales of 1 : 250,000 or even 1: 125,000 there is no appreciable error.
As regards instruments, the Astrolabe 4 Prisme is being increas- ingly used for taking equal altitude observations with most excellent results, but at the present time the 5 in. transit micrometer theodolite, already referred to, is perhaps all that is required for general work. It has now been thoroughly tested and found most satisfactory. As regards smaller instruments, there is the 4 in. tangent-micrometer theodolite, and for rapid exploratory survey, where weight is a great consideration, a little 3 in. theodolite has been found useful.
For baseline measurement the Invar tape should be taken on all serious work, and for filling in the topographical features a good plane-table is doubtless the instrument to use. In mountainous regions and in some other special conditions photographie surveying doubtless has a future before it, and in military operations when the photographs are taken from aircraft it has proved itself invaluable; but in ordinary surveying it is, I think, not likely to take the place of well-established methods. The introduction of wireless telegraphy
Reviews—Professor Sollas—I chthyosawurus Skull. 571
for the determination of longitude is likely to increase in usefulness. Good examples of the work done with it have lately been given in the Geographscal Journal and elsewhere.
REVIEWS.
T—Taer Sxurn or Journos URUS, STUDIED IN SERIAL SECTIONS. By Professor W. J. Sotras, F.R.S. Phil. Trans., ser. B, vol. ceviii, pp. 63-126, with 22 text-figures and 1 plate, 1916.
N this paper Professor Sollas gives a detailed account of the results of his method of serial sections applied to the skull of an Ichthyosaur, probably a variety of J. communis. No less than 520 sections were prepared, photographed, and modelled in wax, and the resulting reconstruction gives a clearer idea of the details - of the structure of the skull than has hitherto been attainable. The relations of the roofing bones of the skull, that unite by extensively overlapping sutures, are now for the first time made clear, and the presence of a septo-maxillary element is demonstrated ; in the lower jaw the presence of the gonzale (prearticular) is shown.
Professor Sollas has met with the usual difficulty in determining the relative position of the bones forming the auditory capsule, the existence during life of extensive areas of cartilage between them resulting in their displacement when putrefaction took place. He puts the pro-otic low down, below the opisthotic and in contact with the basi-occipital, a position which seems inconsistent with the share which this element must have taken in helping to enclose the auditory labyrinth.
Another point of special interest is the presence of a series of structures which are regarded as the remnants of a hyobranchial apparatus. Not only is this interpretation an improbable one, but the facts seem capable of a simpler explanation. The elements (marked a and 6 in fig. 17) which are regarded as branchials closely resemble in form the upper bifurcated ends of cervical ribs, while those marked s.d. may be halves of a neural arch. Professor Sollas admits that these bones lie dorsal to the hyoids, and further- more notes the presence in the specimen of the displaced centra of the atlas, axis, and third cervical, so that it therefore seems at least possible that the presumed branchial bones are displaced appendages of these vertebra.
The paper is illustrated with twenty-two text-figures, mostly of sections of the skull, and a plate giving figures of the basi-occipital and basisphenoid, both of the reconstructed skull and of other specimens. Some diagrammatic figures of the various bones might have been added with advantage.
The paper as a whole is a valuable contribution to our knowledge, and the author is to be congratulated on the successful application of his elaborate and laborious method of investigation to a fresh subject.
C. W. A.
572 Reviews—Prismatic Structure in Igneous Rocks.
«& Ii.—Tyrrs or Prismatic SrrucrurE in Icneous Rocxs. Journ. Geol., vol. xxiv, pp. 215-34, 1916.
(J\HERE are several types of prismatic structure, due to different
causes. Of these the most important are attributed to (1) thermal contraction in the crystallized rock, (2) convectional circulation of the still liquid magma, (3) internal expansion. The study of the prismatic structures in rock-masses may yield useful information as to the conditions under which the rock was formed: since quantitative data are very scarce, it is highly desirable that experimental work in this direction should be carried out; this would necessitate the handling of larger masses of rock than are generally dealt with in laboratory experiments. It is probable that much could be learned from a careful study of such structures in the field. R. H, RB.
JIi.—Tuer Age or tae Kitrarney Granite. Department of Mines, Canada, Museum Bulletin No. 22, 1916.
N this paper Mr. W. H. Collins brings forward evidence to show that the Killarney batholith on the north side of Lake Huron is intrusive into sediments of the Bruce and Cobalt series of the Huronian system. These have undergone a very high degree of deformation and metamorphism, but their correlation with the more normal rocks is established. The granite is not foliated and approaches a syenite in composition, owing to scarcity of quartz, and it contains recognizable xenoliths of the Espanola quartzite and other rocks, thus establishing its post-Huronian age. The disturbance and intrusion were completed long before Ordovician time, and must
therefore be regarded as belonging to the later pre-Cambrian.
RE
1V.—Tue Rocks anp Minerats or tHE Croypon ReeronaL SurvEY ArEA. By G. M. Davirs. Proc. and Trans. Croydon Nat. Hist. and Scient. Soc., 1915-16, pp. 53-96.
OR some years past this society has been conducting a nes survey of Kast Surrey and West Kent. The results of much patient work on the rocks of the district are here presented. The methods adopted are based on ‘panning’ of the material with subsequent separation in heavy liquids, and the data obtained are given in.a quantitative form. The minerals found are those usually present in sedimentary rocks of all ages, and it is clear that there ’ has in all cases been a passage of mineral grains from one bed to another, so that there is less variation in composition than might be expected. Andalusite is found to be fairly common in Cretaceous strata as well as in the Tertiary sands, while the occurrence of monazite is of considerable interest. As might be expected, zircon, tourmaline, and kyanite are almost universally present in the heavy residues, while staurolite and garnet are almost equally common.
R. H. BR.
Reviews—Metals 1n Pre-Cambrian of Ontario. 578
V.—Merattoeeneric Epocus 1n THE PRe-CamBrian oF Ontario. By W. G. Minter and C. W. Kyieur. Trans. Roy. Soc. Canada, ser. ul, vol. ix, pp. 241-9, 1915.
HE enormous economic importance of the ore bodies of Ontario has enabled geologists to study the Pre-Cambrian rocks there disclosed with very special intimacy. While only a few years ago Lindgren found it advisable to consider the Pre-Cambrian era of ore deposition as a whole, the authors of the paper before us have distinguished four major epochs of metallogenesis. The following table summarizes the main conclusions :— :
Keweenawan.—Basic intrusions passing in places into acid rocks. 1. Silver, cobalt, nickel, and arsenic at Cobalt. 2. Nickel and copper at Sudbury. 3. Gold deposits (not now productive).
Animikean.—Chemical deposition of ‘iron formations ’. Algoman.—Intrusions of granite.
1. Gold at Porcupine and many other localities.
2. Galena, zincblende, and fluorspar.
Basic intrusions of post-Timiskamian age. 1. Nickel and chromite. 2. Magnetite and titaniferous magnetite.
Timiskamian.—Chemical deposition of ‘iron formations’ (of minor importance). Laurentian.—Intrusions of granite (which probably gave rise to ore deposits since removed by excessive erosion). Grenville.—Chemical deposition of ‘iron formations’. Keewatin.—Extrusions of basic volcanic rocks.
The table brings out the importance of igneous activity in the formation of ore deposits, the succession including three cycles of intrusion each beginning with basic and concluding with acid rocks. At present the ‘iron formations’ of Animikean and Timiskamian -age.in Ontario are not productive, but in Michigan they are the annual source of millions of tons of iron-ore.
AGSHC
VI.—GuiIpE-B00K oF THE WestERN Unitep States. Part C: Tue Santa Fe Rovre. Bull. 613 U.S.G.S. pp. 194. Washington, 1915.
({X\HIS book, which is one of a series of four dealing with the main
railway routes in the western United States, is issued with a view to furthering the ‘‘ see America first”? movement, by providing a handy book which will give the traveller all the important features, both geological and geographical, in order, as he journeys along the railway. The book is divided up into sections, each with its own map showing the railway and the country from ten to fifteen miles on either side of it, with contours and geological boundaries. Each section covers about sixty miles, the whole route stretching from Kansas City to Los Angeles, and including a journey to the Grand
574 Reports & Proceedings—Geological Society of London.
Canon of the Colorado. A short history is given of the different states and towns through which the line passes, as is also an account of their agricultural and mineral resources, while the geological and geographical features are described in some detail in their order. The book is illustrated by a series of excellent photographs and many geological sections ; it has also a useful index of the stations.
Wi Ewe
REHPORTS AND PROCHEDINGS-
I.—Gerotoaicat Soctrry oF Lonpon.
November 8, 1916.—Dr. Alfred Harker, F.R.S., President, : in the Chair.
The President referred to the loss which the Society had sustained during the recess by the decease of its Treasurer, Mr. Bedford McNeill, A.R.S.M., M.Inst.M.M., A.M.Inst.C.E. | He spoke of Mr. McNeill’s eminence in his profession, and of the services that he had rendered to the Society as a Member of Council for many years and as Treasurer since 1912. The President mentioned that the Society was well represented at the funeral, and added that he felt sure that the Fellows would associate themselves with the resolution of condolence and sympathy which the Council had addressed to Mrs. McNeill.
The following communication was read :—
‘‘ dulina rotiformis, gen. et sp. uov., Phillipsastrea hennahi (Lonsdale), and the genus Orionastrea.’’ By Stanley Smith, B.A., D:Se., 2 .G:s:
The primary object of the present communication is a description of a new and interesting coral genus of colonial habit, Aula, obtained from the highest limestone that can be associated with the Lower Carboniferous—the Fell Top Limestone of Northumberland and its equivalent horizon in Teesdale, the Botany Beds.
Since this form has been confounded with another Carboniferous species well known under the name of ‘ Phillipsastrea radiata (S. Woodward)’, it has been found advisable, in fact necessary, to extend the original scope of the paper so as to include a revision of the genus Phillipsastrea and a description of ‘ Ph. radiata’ and its allies, which I have grouped together under a new generic name, Orionastrea. Several type-specimens, including that of Phillips- astrea hennahi (the genotype of Phillipsastrea), are described and figured.
The new genus from the Fell Top Limestone is a very distinctive form, on account of the remarkable annular wall developed within the theca, and may prove of considerable value as a zonal index.
Reports & Proceedings—Mvneralogical Society. 575
The corallum in this genus, as also in Phillipsastrea and in Orionastrea, represents a stage in colonial development in which the epitheca of the individual corallites has entirely disappeared, and these are consequently united by their dissepimental tissue—a type of colony to which the term ‘ Astreiform’ may be applied.
Diacnoszs.—Aulina rotiformis.—The corallum is massive, and the corallites are united by their extrathecal tissue; all the septa dilate at the theca, and those of the major cycle again dilate at their axial edges, in such a manner as to fuse together, and so build a cylindrical wall or tube within the theca. The structure of the form is in most respects similar to that of Phillipsastrea, but it appears to carry forward the septal characters peculiar to that genus to a further stage of development.
Phillipsastrea.—The corallum is composite and massive ; the corallites are united by their dissepiments, or are only separated by a thin epitheca; in the former case the septa are often confluent. Major and minor septa dilate at the theca; the latter terminate there, and the major septa attenuate and advance into the intrathecal region, and there often dilate again at the axialedge. The central part of the corallite is occupied solely by tabule.
Orionastrea.—The characters of this genus are essentially those of Inthostrotion, but of a modified form. The corallum is composite and massive, and the corallites are either defined by a thin epitheca, or, in the more typical instances, by no epitheca at all; in this latter ease the corallites are united by their dissepiments and the septa are confluent.
The distinguishing characters of the three species recognized and described are as follows :—
1. O. ensifer (Edwards & Haime) . Septa not confluent. Columella present. 2. O. phillipsi (McCoy) . . . . Septaconfiuent . . Columella present. 3. O. placenta (McCoy) . . . . Septaconfluent . . Columellaabsent.
II].—MrneratocicaL Society.
Anniversary Meeting, November 7, 1916.—W. Barnow, F.R.S., Presi- dent, in the Chair.
The following were elected Officers and Members of Council: President, Mr. W. Barlow, F.R.S.; Vice-Presidents, Professor H. L. Bowman, Mr. A. Hutchinson; Treasurer, Sir William P. Beale, Bart., K.C., M.P.; General Secretary, Dr. G. T. Prior, F.R.S.; Foreign Secretary, Professor W. W. Watts, F.R.S.; Editor of the Journal, Mr. L. J. Spencer; Ordinary Members of Council, Captain W. Campbell Smith, Dr. J. W. Evans, Dr. F. H. Hatch, Mr. J. A. Howe, Mr. T. V. Barker, Mr. G. Barrow, Professor C. G. Cullis, Mr. F. P. Mennell, Mr. H. Collingridge, Mr. T. Crook, Dr. G. F. Herbert Smith, Dr. H. H. Thomas.
The following papers were read: Dr. J. W. Evans: The Combina- tion of Twin Operations. The question of complex twin-crystals in which two distinct laws of twinning are represented was dealt with.
576 Obitwary— Bedford McNeull.
A distinction was made between cases in which the twin-axes are parallel or at right angles, and those in which they are inclined to one another obliquely. In the former the result of the combination is itself a twin operation, while in the latter it is a rotation, the direction of which depends on the order in which the operations are applied; it is in some cases combined with an inversion.— Dr. J. W. Evans: A Modification of the Kohlrausch Method of determining Refractive Indices. The observing instrument is a microscope placed vertically and fitted with a Bertrand lens. An immersion theodolite stage of the Klein type is used, so that the substance under investigation may be rotated beneath a liquid of higher refractive index about two axes, the first at right angles to the optical axis of the instrument, and the second at right angles to the first and to the plane surface of the object. This is observed through the natural surface of the liquid and rotated in either direction until the position of total reflection is reached. By rotation of the object about the second axis the refractive indices in all directions parallel to its plane surface may be determined, and the values of the principal refractive indices thus obtained.—A. Holmes and Dr. H. F. Harwood: The Basalts of the Brito-Arctic Province. The basalts from Hare Island, which were collected by Thomas Reid in 1855, include six varieties, of which four are free from olivine and carry silica among the amygdale minerals, and the remaining two contain olivine and are without free silica. All the rocks are rich in titaniferous magnetite, and analyses indicate that their most note- worthy feature is the unusual abundance of titania. The analyses cannot be closely matched except by those of basalts from Scoresby Sound, Iceland, the Farde Islands, and the west of Scotland. This paper is the first of a series in which the authors hope to describe rocks from all the important localities within the province.—Miss N. Hosalie exhibited models of crystals constructed by herself.
OBITUARY -
BEDFORD McNEILL
A.R.S.M., M.Inst.M.M., Assoc. Mrmr. Iysr.C.E., TREASURER Grou. Soc. Lonp., Erc.
By the death of Mr. Bedford McNeill, at the comparatively early age of 55, the mining world has lost one of its most distinguished men. Mr. McNeill took his diploma at the Royal School of Mines in 1880, and after considerable experience in various parts of Europe and America became famous as the compiler of ‘‘the Telegraphic Code”’ that bears hisname. He gave his time freely to the service of scientific societies, and besides being a Fellow of the Institute of Chemistry and a Member of the Iron and Steel Institute, he was President of the Institution of Mining and Metallurgy 1913-14, and Treasurer of the Geological Society from 1912 until the time of his death.
INDEX.
CID Rocks of Iceland, 468. Actinacis martlandi, n.sp., 529. sumatraensis, 530.
Age of Human Race, 285.
Agricultural Geology, 474.
Alpine Chain, Crystalline Schists, 505.
Alps and Apennines, Contact-Zone of, 400.
American Bison antiquus, 283.
Carboniferous Fauna, 282. Ammonite Celoceras Dave@i, 196. Ampthill and Oxford Clays, 395. Analcite and Analcitation, 41. Ancient Shore-line, 138.
Andrews, C. W., Skeleton of Steno- mylus hitchcocki, 1; Carinate Bird, Nigeria, 333.
‘Anniversary, Geological Society, 135. Anthracite, Origin, Distribution of ,220. Antiquity of Man, 32, 527.
Arctic Flora in Pleistocene Beds, Cambridge, 339.
Arran Pitchstones, 469.
Artesian Water in Manitoba, 219.
Ashdown Sand, 295.
“ Asterolepis ornata, var. australis,”’ Generic Position of, 373.
Atlantic, North, Volcanic, Plateau, 385.
Atwood, W. W., Eocene Boulder- - clay, Colorado, 329. Aulinarotiformis, gen. etsp. nov.,574. Axinite Veins in Penmaenmawr
Porphyrite, 5.
AILEY, EH. B., The Islay Anti- cline, 133. :
Ball or Pillow-form Structures in Sandstone, 146.
Barlow, W., Crystallographic Rela- tions, 44.
Barrell, J., Strength of the Earth’s Crust, 38.
Basalts, Brito-Arctic, 576.
Bassler, R. S., Bibliographic Index of American Fossils, 325.
Bate, D. M. A., Anserine Bird Remains, Malta, 332.
Bather, F. A., Studies in Edrio- asteroidea, 37; Cidarid from Hart- well Clay, 303.
Bay of Fundy, Marine Fauna, 379.
Raindrops recorded, 546.
Becker, G. F., Isostasy and Radio- activity, 88.
DECADE VI.—VOL. III.—NO. XII.
Bedson, P. P., Proximate Constituents of Coal, 514.
Bennettitean Cones, Cretaceous, 380. Bibliographic Index, American Ordo- vician and Silurian Fossils, 325. Bibliography of Natural History, 282.
Bird-bones from California, 283.
Malta, 332.
—— Nigeria, 333.
South Carolina, 343.
Birth-time of the World, etc., 176.
Bolton, H., Fossil Insects, British Coal-measures, 235.
Bone, W. A., Discussion ‘on Coal, 512.
Bonney, T. G., Age of Carrara Marbles, 47; Glacier Lake Channels, 141; Overflow Channels from Frozen Lakes, 229; Crystalline Schists of Piedmont, 505.
Boone Chert and Limestone, Arkansas, Fauna of, 378, 379.
Borings in Tertiary of Victoria, Australia, 281.
for Water, Leicester, 68, 456.
Boswell, P. G. H., Quantitative Methods in Stratigraphy, 105, 1638; Petrology of North Sea Drift, 334 ; Glass Sands, 466.
Boulton, W. S., Discussion on Coal, 518; Address to Section C, British Association, 550.
Bournemouth, Physical Geography of, 133.
Bowen, N. L., Evolution of Igneous Rocks, 469.
Brachiopod Morphology, 21, 496.
Brazil, Parahyba and Rio Grande, 523.
Brighton’s Lost River, 41.
Brines, Manitoba, Corrosive Action, 31.
British Association, Coal Discussion, olla
—— Address, Section C, 550.
—— Address, Section E, 564.
Titles of Papers, 464.
British Fossil Insects, 235, 282.
Broom, R., Skull Chrysochloris, 333.
Brydone, R. M., New Chalk Polyzoa, 97, 241, 337, 433.
Burling, L. D., Faunistic Influence,
181; Shallow-water Deposits in Cambrian, 181. Bury, H., Physical Geography, Bournemouth, 133. 37
4
578
ADELL, H. M., Klondike and Yukon Goldfield, 89.
Cader Idris, Ordovician in, 30.
Cairo, Subsoil of, 39.
Calcium Carbonate and Evolution in Polyzoa, 73.
Californian Paleontology, 283.
Pliocene, 284.
Cambrian of Canadian Cordillera, 181.
Canada, Economic Geology of, 87.
Cantrill, T. C., South Wales Coal- field, 274.
Canu, M.F., French Tertiary Polyzoa, 376.
Carboniferous Fossils, Siam, 284.
Carrara Marble District, 92.
Marbles, Geological Age of, 47.
Cassiterite, Malaya, 255.
San Diego, California, 429.
Cephalopod, Mandible of Giant, 260.
Cesaro, C., Demonstration of Law of Millar, 139.
Chacko, I. C., Cordierite, 462.
Chalk Polyzoa, 97, 241, 337, 433.
Channels from Glacier Ice-dammed Lakes, 26, 45, 77, 229.
Chapman, F., Hqwisetites wonthag- giensis, 2325; Victorian Trilobites, 232; Cainozoic of Mallu and Vic- torian Bores, 281 ; Generic Position of “ Asterolepis ornata, var. aus- tralis’’, 373.
Chemical Analyses, St. Bees Sand- stone, 17.
Chirosauroid Footprint, Lower Keuper Sandstone, 421.
Chrysochloris, Skull of, 333.
Cidarid from Hartwell Clay, 302.
Cimolestes cutleri, A. S. Woodw., sp. noy., 333.
Clark, W. B., Mesozoic and Cenozoic Echinodermata, 277.
Clarke, F. W., Inorganic Constituents of Echinoderms, 231.
Climate of Geologic Time, 129.
Closing of National Geological Collec- tions, 192.
Clough, C. T., Obituary of, 525.
Coal and Coal Resources, Canada, 87.
Coal Discussion, British Association, Newcastle, 511.
Coal Resources, Canada, 232.
Coalfields, Present and Future, 550.
Coal-measure Amphibia and Crossop- terygia, 35.
Coals of South Wales, 220.
Coastal Changes, Factors in, 188.
Caloceras Davai, rectiradiatum, var. noy., W. Wingrave, 196.
Index.
Collins, W. H., Age of Killarney Granite, 571.
Contact-Zone of Alps and Apennines, Liguria, 400, 447, 489.
Cope, T. H., Igneous Rocks, North Wales, 90.
Corals, Eocene, New Guinea, 482.
Cordierite, Optically Positive, 462.
Correlation of Potassium and Mag- nesium, etc., 233.
Corrosive Action of Brines, 31.
Cotton, C. A., Geology of New Zealand, 243, 314.
Cottonwood—American Fork, Survey of, 428.
Cox, A. H., Ordovician, Cader Idris,30.
Crag Mollusca, British, 472.
Cranbrook Map, British Columbia, 523.
Cretaceous Lamellibranchiata, Cata- logue of British Types, 37.
Crick, G. C., Gigantic Cephalopod ‘Mandible, 260.
Cross, W., Lavas of Hawaii, 89.
Crystalline Rocks, Northern Piémont, 198, 250, 304, 348, 505.
Crystallographic Relations of Allied Substances, 44.
DA CHIARDIA macgregorz, 486. Dallas, J., Obituary of, 477.
Dana’s System of Mineralogy, 326.
Davies, A. M., Oxford and Ampthill Clays, 395.
Davies, G. M., Rock and Minerals, Croydon, 572.
Dawson, Charles, Obituary of, 477.
Day, T. C., Veining in Basalt, Upper Whitfield, 137.
Deeley, R. M., Trail and Underplight, 2; Fluvio-glacial Gravels, Thames Valley, 57; Thames Valley Gravels, 111; Isostasy, 323; Ice Age and Glacier Fluctuations, 536. j
Delta Deposits of the Nile, 39.
Demonstration of Law of Millar, 139.
Desch, C. H., Origin of Agates, 525.
Determinative Mineralogy, 179.
Dewey, H., River Gorges in Cornwall and Deyon, 234.
Diamond, Origin of, 327.
Diatomaceous Deposit, Loch Leven, 136. :
Dickerson, R. E., Tejon Cretaceous, California, Fauna of, 377.
Differentiation in Igneous Rocks, 189.
Dinosaurs in Bushmanland, 283.
Doelter’s Handbook of Mineralogy, 39.
Dowling, D. B., Coal-fields, Canada, 232:
Draper, D., Origin of Diamond, 327.
Index.
Drought in Waterberg, Effects of, 129.
Dunean, J., Diatomaceous Deposit, Loch Leven, 136.
Dunn, J. T., Discussion on Coal, 512.
ALING Scientific Society, 519. Karth, Form and Constitution of, 180. Internal Structure of, Mechanical Properties and Viscosity of, 126. Earth’s Crust, Strength of, 38. Thermal History, 265. East Lothian, 232. Echinid Faunas in Eocene Heypt, 64. Neogene Formations, 355. Hehinodermata, Inorganic Constitu- ents of, 231. Mesozoie and Cenozoic, U.S.A., 277. Hidestus, Upper Carboniferous, York- shire, New Species, 381. Edinburgh Geological Society, 136, 137, 188. Edrioasteroidea, Studies in, 37. Elasmobranch Teeth, Russia, 373. Eminent Living Geologists: Marr, J. H., 289. Engineering Geology, 278. Eocene Corals, New Guinea, 481,529. —— of Egypt, Echinid Faunas, 64. —— Glacial Deposits, Colorado, 329. Epigene Profiles of Desert, 180. Hquisetites, Jurassic, Victoria, 232. Eramosa Beds, 128. Erosion Phenomena in Egypt, 334. Hurypterid Horizon, New, 128. Evans, J. W., Directions-image, How to obtain, 44; Differentiation in Igneous Rocks, 189; Laws of Twinning, 335, 575. Extinct Bird, Malta, 332. Nigeria, 333. —— South Carolina, 343.
AUNA of Batesville Sandstone, N. Arkansas, 280. Faunas of Tejon EKocene and Cre- taceous, California, 377. Faunistic Influence on Lithology, 181. Fearnsides, W. G., On Coal, 517. Fens, 283. Ferruginous Nodules, Permo-Triassic Sandstone, 286. Field Analysis of Minerals, 178. Fischer, Dr. P. M. H., Obituary, 432. Fletcher, S. L., Meteorites, 519. Fleit, J. S., Swiney Lecturer, 528. Flints in Sedgwick Museum, 34. _ Fluvio - glacial Gravels, Thames Valley, 57, 111.
579
Ford, W. E., Appendix to Dana’s Mineralogy, 326.
Former Courses of River Devon, 137.
Fossil Collecting, 379.
Insects, British Coal, 235.
— Mammals, China, 127.
Wood, method of hardening, for sections, 142.
Fourtau, R., Hocene of Egypt, Echinid Fauna, 64, 355.
Foye, W. G., Nepheline-syenites, Ontario, 524.
ARDNER, EH. W., Pleistocene
Beds, Barnwell, 339. Gazelle-Camel, Stenomylus Hitch- cockt, 1.
Geikie, Jas., Biography of, 477.
Geitsi Gubib, an old voleano, 522.
Geological History, New Zealand, 243, 314.
Protractor, 233.
Geological Society, Edinburgh, 136, 187, 188.
Glasgow, 41, 138, 239, 285, 335,
524.
Liverpool, 90, 139, 286.
— London, 42, 44, 132, 133, 134, 135, 182, 234, 235, 236, 237, 284, 330, 332, 381, 574.
Geological Survey, Great Britain, 220, 274, 423, 430, 521.
— New Zealand, 328.
—— Portugal, 329.
— Sweden, 384.
— United States, 427.
Western Australia, 228.
Geologists’ Association, 181, 334.
Geology of To-day, 81.
Text-Book of, 424.
Geophysical Laboratory, 426.
Giant Beaver, from Pleistocene, 322.
Gigantic Carinate Bird, lHocene, Nigeria, 333.
Gilpin County, Colorado, Geology, 429.
Girty, G. H., Fauna of Batesville Sandstone, 280; Fauna of Boone Chert, Arkansas, 378.
Glacial Anticyclone, 130.
Geology, North America, 281.
Glacier Fluctuations and Ice Age, 536.
Lake Channels, 26, 45, 77, 141.
Glass Sands, 466.
Glen Lednock, Physiography of, 138.
Gold Deposits, Quartzite, Arizona, 427.
Grainsgill Greisen, Carrock Fell, 239.
Granitic Rock, Malay States, 441.
Greenstones of Piémontese Alps, 156.
Greenwood, H. W., Origin of Trias, 139; Triassic Rocks of Wirral, 180.
580
Gregory, J. W., Geology of To-day, 81; Age of Norseman Limestone, 320 ; Pseudo-Megalithic Tor, 335; Eocene Corals, New Guinea, 481, 529.
Guppy, R. J. L., Obituary of, 479.
ALL, T.S., Obituary of, 144. Harmer, F. W., Crag Mollusca, 472.
Harwood, H. F., Basalts of Brito- Arctic, 576.
Hawkes, L., Tridymite in Icelandic Rocks, 205; North Atlantic Voleanic Plateau, 385; Acid Rocks of Iceland, 468 ; Ropy Lava Surfaces, 476.
Hawkins, H. L., Lovenia forbesi, 100.
Hay, O. P., Pleistocene Mammals, Towa, 35.
Hayes, A. O., Wabana Iron Ore, 90.
Healdton Oil-field, Oklahoma, 429.
Heterangiums of British Coal- measures, 123.
Hickling, G., Nature of Coal, 517.
Himalaya, Support of, 134.
History of Coal, 1672, 136.
Hobbs, W. H., Glacial Anticyclone, 130.
Hoepen, EH. O. N. van, Stegocephalia of Senekal, 83.
Holland, Sir T. H., Minerals, India, 40.
Holmes, A., Interior of Karth, 126; Karth’s Thermal History, 265; Tertiary Volcanic Rocks, Mozam- bique, 382; Basalts of Brito-Arctic, 576.
Horwood, A. R.,. Upper Trias, Leicestershire, 360, 411, 456.
Huene, von, Muschelkalk Ichthyo- saurs, 476.
Hughes, T. McKenny, The Fens, 283.
Human Skeleton in supposed Glacial Deposits, 527.
Hume, W. F., Nitrate Shales of Egypt, 328.
CE Age and Glacier Fluctuations, 536. Ichthyosaurus Sections, 571. Igneous Rocks, Berwyn Hills, 90. Rocks, Evolution of, 469. Indarch, Russia, Meteorite fall, 40. Indian Geology, 380. Interambulacrals, Loveniaforbesi,100. Interior of Harth and Moon, 126. Tron-ores, Texas, 428. Islay, Anticline (Inner Hebrides), 133. Isostasy, 323. and Asthenosphere, 38. and Radio-activity, 88.
Skull in Serial
Index.
ACKSON, W. J., on Thomson’s Brachiopod Morphology, 21. Jeffreys, H., Interior of Earth and Moon, 126; Mechanical Properties of Earth, 126 ; Viscosity of, 126. Jehu, Lewd Obscure Factors in Coastal Changes, 188.
Johnston, J., Pressure in Formation of Rocks, 233.
Johnston, M. A., Erosion Phevomen Egypt, 334.
Joly, J., Birth-time of the World, 176
Jones, D. Trevor, Chemical Composi- tion of Coal, 514.
Jones, T. A., Ferruginous Nodules, Permo-Triassic, 286.
Jones, W. R., Topaz and Cassiterite in Malaya, 255; Tin, Malay, 453.
Jones, W. Rupert, Obituary of, 96.
Jubaland, East Africa Protectorate, 42.
Judd, J. W., Obituary of, 190.
ARPINSKY, Helicoprion, 373. Kegworth Footprint, The, 421. Keith, A., Antiquity of Man, 32, 527. Kendall, P. F., Glacier-Lake Channels, 26, 77; Ash in Coal-seams, 512. Kier, J., Fish Remains, Ellesmere Land, 372. Killarney Granite, Age of, 572.. Kindle, E. M., Silurian of Lower Saskatchewan, 132; Dredging in Bay of Fundy, 379; "Fossil Collect- ing, 379; Small Pit and Mound Structures, 542. Klondike and Yukon Goldfield, 89. Knight, C. W., Pre-Cambrian, Ontario, 573. Kobya hemicribriformis, n.g. & sp., 487.
AKE District Geology, 374.
Land of Deep Corrosions, 209. Lang, W. D., Evolution in Polyzoa, 73. Lavas of Hawaii, 89.
Laws of Twinning, 335.
Lawson, A. C., Epigene Profiles of Desert, 180 ; Pre-Cambrian Rocks, Canada, 475.
Lebour, G. A., Coal Discussion, 511.
Leicestershire, Upper Trias of, 360.
Leptoria carnet, n.sp., 485.
Lewis, J. V., Mineralogy, 179.
Liassic Fish, Sawrostomus esocinus,49.
Liguria, Ophiolithic Rocks, 447, 489.
Liverpool Geological Society, 139.
Lovenia forbesi, Australia, 100.
Lurgecombe Mill, Lamprophyre, 284.
Index.
ACDONALD, D. F., Geology of Panama Canal, 521.
Macgregor, M., Ancient Shore-line, 138.
MecGrigor, G. D., Field Analysis of Minerals, 178.
Mechean, A., Age of Human Race, 285.
MeNeill, Bedford, Obituary, 574, 576.
Malay States, Geology of, 125.
Malcolm, W., Oil and Gas Fields, Ontario and Quebec, 232.
Malm6é, Sweden, Prehistoric Flint- mines, 34.
Mammoths and Mastodons, 128.
Man, Antiquity of, 32, 527.
Mapping Harth’s Surface, 564.
Marr, J. E., Geologist, 289; Pleisto- cene Beds, Barnwell, 339 ; Geology of Lake District, 374.
Matsuomoto, H., Fossil Mammals, China and Japan, 127.
Matthew, W. D., Mammoths and Mastodons, 128.
Melmore, S., St. Bees Sandstone, 17.
Membranipora cubitalis, sp. nov., R. M. Brydone, 434.
cupolata, n.sp., Brydone, 242.
demissa, n.sp., Brydone, 98.
—— Fania, n.sp., Brydone, 241.
—— flucnia, n.sp., Brydone, 433.
fonteia, n.sp., Brydone, 434.
—— fulgora, n.sp., Brydone, 434.
—— furina, n.sp., Brydone, 435.
mussilis, n.sp., Brydone, 241.
obscurata, n.sp., Brydone, 99.
pontifera, u.sp., Brydone, 99.
— Studlandensis, n.sp., Bryd., 97.
subacuminata, n.sp., Bryd., 97.
— vectensis, n.sp., Brydone, 242.
—— Woodwardi, Bryd., var. pin- guescens, var. noy., 98.
Merriam, J. C., on Pliohippus pro- versus, 283; Miocene Vertebrates, Nevada, 284.
Mesozoic and Cenozoic Echinoder- mata, U.S.A., 277.
Mactrine, North America, 376.
Orogenic Movements, New Zealand, 243.
Metallogenetic Epochs, Pre-Cambrian, Ontario, 573.
Meteorites, Lecture on, 519.
Russian, 40.
Mexican Geology, 380.
Milford, Geology of Country round, 274.
Miller, L., Fossil Birds, California,283.
Milier, W. G., Pre-Cambrian, Ontario, 573.
Mineral Production, India, 40.
581
Mineral Resources of Britain, 224, 430.
of Philippine Islands, 89.
Mineralogical Society, 44, 139, 238, 335, 575.
Mineralogy, Doelter’s Handbook of, 39.
Elements of, 179.
Miocene Vertebrates, Nevada, 284.
Moberg, J. C., Obituary of, 96.
Moir, J. R., Late Horizon of Ipswich Skeleton, 527.
Montipora antiqua, n.sp., 531.
Moodie, R. L., Amphibia of Coal- measures, 35.
Morgan, P. C., Geological Survey, New Zealand, 328.
Muir, T. 8., Hast Lothian,-232.
Muschelkalk Ichthyosaurs, 476.
Museum Practical Geology, Onn losee Lamellibranchiata, 37.
AUTILUS (Rhyncholithes butleri n.sp.) sp., G. C. Crick, 262.
Neogene, Hechinid Fauna, 355.
Nepheline-syenites, Ontario, 524.
New Guinea Fossil Corals, 481, 529.
Geology, 380.
New York State Museum, Paleozoic Fishes, 36.
New Zealand, Geological Survey of, 328.
Structure of, 243, 314.
Newton, E. Tulley, Trogontheriwm, Pleistocene, 322.
Nicholas, R. H., Tabular Southampton, 372.
Nitrate Deposits, Idaho and Oregon, 427.
Shales of Egypt, 328.
Nomland, J. O., Lower Fliocene, California, 378.
Norseman Limestone, W. Australia, Age of, 320.
Flints,
BITUARY Notices: Clough, Dr. C. D., 525; Dallas, Jasl, 477;
Dawson, Chas., 477; Fischer, Dr. Pp. M. H., 432; Guppy, R. J. L., 479; Hall, Dr. T. S., 144; Jones, W. Rupert, 96; Judd, Professor J. W., 190; McNeill, Bedford, 576; Moberg, Dr. J. C.; 96; Ramsay, Sir William, 384; Smith, E. A., 431; Solms-Laubach, Count zu, 143; Valentine, Lieut. R. L., 287 ; Vaughan, Dr. A., 48.
Obsidian, Structure of, Iceland, 182.
Obsidianites from Raffles Museum, Singapore, 145.
Oil and Gas Fields, Quebec, 232.
Ontario and
582
Oldham, R. D., Support of Himalaya, 134.
Ophiolithic Rocks, Liguria, 447, 489.
Ordovician in Cader Idris, 30.
Ore Deposits, Alaska Peninsula, 230.
Origin of Agates, 525.
of Trias, 139.
Orionastrea, 574.
Oxford and Ampthill Clays, 395.
ACKARD, E. L., Mactrine of Pacific Coast, 376. Pale@ocheniides mioceanus, gen. et sp. nov., R. W. Shufeldt, 347. Paleoliths of Kansas, 35. Paleontographical Society, 472. of Petrograd, 384. Paleozoic Fishes, New York State Museum, 36 Fossils of Burma, Lower, 225. Panama Canal, Geology, 521. Parapavo calvfornicus, 283. Parkinson, J., Structure of Jubaland, EK. Africa, 42.
Parry, T. W., Tyrephining a Pre- historic Art, 372.
Penmaenmawr Porphyrite, Axinite Veins in, 5.
Pennines, Northern, Structure of, 547.
Percival, F. G., Punctation of Tere- bratulid Shells, 51.
Permian in Alps of Piémont and Savoy, 7.
Petrography of Arran, 193.
of South Georgia, 435.
Petrological and Quantitative Methods in Stratigraphy, 105, 163.
Petrology of North Sea Drift, 334.
Philippine Islands, Minerals of, 89.
Phillipsastrea hennahi, 574. :
Pickering, A. J., Water-borings, Hinckley, 68.
Picrite-Teschenite Sill of Lugar, 237.
Piémont Alps, Crystalline Rocks of, 198, 250, 304, 348.
Dauphiné and Savoy, 7
“*Pietre Verdi,’’ Piémontese Alps, 156.
Pillow Structures in Sandstone, 146.
Pirsson, Louis V., Text-Book of Geology, 424.
Pit and Mound Structures through Sedimentation, 542.
Pitchstone Xenoliths in Basalt, Arran, 193.
Pleistocene Beds, Barnwell, Arctic Flora, 339.
Fossil Mammals of China and Japan, 127.
Indiana and Michigan, 281. -—— Mammals, Iowa, 35.
Index
Plesiastrea horizontalis, n.sp., 486.
Pliocene Fauna, California, 378.
Floras of Dutch - Prussian
Border, 227.
Mollusca, Great Britain, 472.
Pliohippus proversus, 283.
Pneumatolytic Alteration of Granite, 441,
Polyzoa, Calcium Carbonate in, 73.
New Chalk, 97, 241, 337, 433.
Porcupine, Geology of, 124.
Porites _ deshayesana, Mich., mequisepta, var. noy., 530.
Porosity of Rocks, Karoo System, 41.
Portugal, Geological Survey, 329.
Pre-Cambrian, Great Lakes, 475.
Ontario, 573.
Prehistoric Archeology, 34, 527.
Preller, C. S. du R., Permian of Piémontese Alps, 7; Carrara Marble District, 92; Pietre Verdi of Pié- montese Alps, 156; Crystalline Rocks of Piémont, 198, 250, 304, 348; Contact-Zone of Alps and Apennines, 400 ; Ophiolithic Rocks, Liguria, 447, 489.
Pressure in Formation of Rocks and Minerals, 233.
Prismatic Structure in inane Rocks, 572.
Pseudo-Megalithic Tor, 335.
Pseudo-Trachylyte of Orange Free State, 236.
Pterostichites grandis, sp. nov., A. R- Horwood, 411.
Punctation of Terebratulid Shells, 51.
Purbeck Charas, C. and EH. Reid, 475.
var.
graphy, 105, 163. Quartz after Tridymite in Icelandic Rocks, 205. Queensland, Geological Notes on, 288.
() sraphy, 105, 1 Methods in Strati-
ACHITOMOUS Stegocephalian, Upper Permian, 83.
Radio-activity and Geology, 176.
and Isostasy, 265.
Ramsay, Sir William, Obituary, 384.
Rastall, R. H., Agricultural Geology, 474,
Red Indians, New Jersey, 34.
Reed, F. R. C., Notes on Trimucleus, 118; On the genus Trinuclews, 169; Lower Paleozoic Fossils, Burma, 225; Carboniferous Fossils, Siam, 284.
Reeves, E. A., Mapping Harth’s face, 564.
Sur-
Index.
Reid, C. and EH., Pliocene Faunas, -Holland, 227; Purbeck Charas, 475.
Relf, F. J., Wealden Sands, 295.
Rhodes, J. EK. W., Former Courses of |
River Devon, 137. Richter, R., Trilobite Harpes, 36. Ries, H., Engineering Geology, 278. River Gorges, Cornwall, Devon, 234. Rocks and Minerals, Croydon, 572. Rogers, A. W., Old African Volcano, 522. : Ropy Lava, Iceland, 476. Royal Society, 330, 380. Russian Palseontographical Society, 384. Rutley, F., Mineralogy, 179.
T. BEES Sandstone, W. Cumber- land, 17.
Santa Fe Route, Western U.S.A.,573.
Sargent, H. C., Axinite Veins in Porphyrite, 5.
Saurostomus esocuvus, fossil fish, 49.
Schofield, S. J., Cranbrook, British Columbia, 523.
Schuchert, Climate of Geologic Time, 129. ,
Scott, A., Analcite and Analcitation, 41; Physiography of Glen Lednock, 138; Arran Pitchstones, 469.
Scott, D. H., Heterangiums of Coal- measures, 123.
Serivenor, J. B., Geology of Malay States, 125; Obsidianites from Singapore, 145; Grainsgill Greissen, 239; Tungsten Ores, 430.
Section-cutting, Fossil Wood, Harden- ing Process, 142.
Sedgwick Museum Notes: Trimucleus, 118, 169.
Sedimentation, Pit and Mound Struc- tures during, 542.
Shand, S. J., Pseudo-Trachylyte of Parijs, 236.
Sheppard, T., Bibliography of York- shire Geology, 131; William Smith’s Maps, 143.
Shufeldt, R. W., Extinct Bird, South Carolina, 343.
Silurian of Lower Saskatchewan, 132.
Singapore, Obsidianites from, 145.
Skiddaw, 90.
Smith, B., On certain Channels, 45; Ball or Pillow-form Rocks, 146.
Smith, Edgar A., Obituary of, 431.
Smith, E. C. Bowden, Subsoil of Cairo, 39.
Smith, H. G., Lurgecombe Lamprophyre, 284.
Mill,
583
Smith, J., Thousand-foot Platform, Arran, 286.
Smith, 8., Awlina rotiformis, gen. et sp. noy., 574.
Smith’s, William, Maps, 148.
Sollas, W. J., Skull of Ichthyosawus in Sections, 571.
Solms-Laubach, H. Graf, of, 143.
Soper, R. H., Parahyba, Brazil, 523.
South Georgia, Petrography of, 435.
Lancashire Coal-field, 430.
Wales Coal-field, Milford, 274.
Stegocephalia of Senekal, 83.
Stenomylus hitchcock, Skeleton of, 1.
Stewart, L. B., Form and Constitution of Earth, 180.
Stopes, M. C., Bennettitean Cones, Cretaceous, 380; Composition of Coal, 515.
Strahan, A., Missenden, 132; Wales, 220.
Stylina macgregori, n.sp., Gregory and Trench, 484.
Stylophora papuensis, n.sp., Gregory and Trench, 483.
Suter, H., Revision of Tertiary Mol- lusea, 231.
Swiney Lectures, Mineral Resources, Europe, 528.
Obituary
Mounted
Coal Boring, Little Coals of South
ABULAR Flint Industry, South- ampton, 372.
Tait, D., Midlothian Coal-field, 136.
Taloai, Darling Downs, Queensland, Human Skull, 44.
Terebratellide, Classification of, 496.
Terebratula, Punctation of Shells, 51.
Termier, P., Eduard Suess, 131.
Tertiary Mollusca, New Zealand, Revision of, 231.
Polyzoa, France, 376.
Voleanic Rocks, Mozambique,382.
Thames Valley Gravels, 57, 111.
Thickness of English Strata, 521.
Thomson, J. Allan, Brachiopod Morphology, 21; ‘Terebratellide, 496.
Thousand-foot Platform, Arran, 286.
Tillyard, R. J., Zoogeographical Regions, Study of, 180.
Tin-mining, Malay States, 453.
Tinne, C., Hardening Fossil Wood for Sections, 142.
Toit, A. L. du, Porosity of Rocks of Karoo, 41.
Topaz and Cassiterite in Malaya, Federated Malay States, 255.
584
Trail and Underplight, 2.
Trench, J. B., Eocene Corals, New Guinea, 482, 529.
Trephining among Primitive Peoples, 372.
Triassic Rocks, Wirral, 180.
Tridymite in Icelandic Rocks, 205.
Trilobite Harpes, Structure of, 36.
Trinucleus, Notes on genus, 118, 169.
Trogontheriwm, Pleistocene, Essex, 322.
Tungsten Ores, 430.
and Manganese in Britain, 224.
Twin Crystals, 575.
Tyrrell, G. W., Petrography of Arran, 193; Picrite - Teschenite Sill of Lugar, 237; Petrography, South Georgia, 435.
Tyrrell, J. B., Geology of Porcupine, 124; Artesian Water, Manitoba, 219.
LU Bakau, Malay States, Tin- mining at, 453. Underplight and Trail, 2. United States Geological Survey, 427 ; Guide-book of, 573. ; Upper Devonian Fish Remains, Hlles- mere Sand, 372. Trias, Leicestershire, 360, 411, 456.
ALENTINE, Lieut. R. L., Obituary of, 287. Vaughan, A., Obituary of, 48, 92. Veining in Basalt, Upper Whitfield, 137. Vertebrate Remains, Cavern, Malta, 332. Vibration Plane of Polariser in Petro- graphic Microscope, 233. Victorian Trilobites (Australia), 232. Viscosity of Harth, 126. Volcanic Necks, N.W. Ayrshire, 239. Plateau, North Atlantic, 385. — Rocks, 8.E. Queensland, 431.
Har Dalam
Index.
ABANA Tron-ore, Newfoundland, 90.
Wallace, R. C., Brines, Manitoba, 31.
Ward, F. K., Land of Deep Corrosions, 209.
Washington, H. §., Correlation of Elements, 233.
Water Borings, Hinckley, Leicester- shire, 68.
Waterberg, Transvaal, Drought, 129.
Water-supply, Exeter, Records on, 520.
Upper Trias, Leicestershire, 456.
Wealden Sands examined, 295.
Wellesbourne, Sussex, 41.
Western Australia, Geological Survey of, 228.
-— Norseman Limestone of, 320.
Whitby and Scarborough Geology, 423.
Willbourn, E. §., Alteration of Granitic Rock, 441.
Wilmore, A., Northern Pennines, 547.
Wilson, G. V., Volcanic Necks, Ayr- shire, 239.
Wingrave, W., Celoceras Davei, rectiradiatwm, var. noy., 196.
Woodward, A. S8S., Specimen of Saurostomus esocinus, 49; Czimno- lestes cutlert, sp. nov., 3383; New Species of Hdestws, Yorks, 381.
Wright, C. W., Ore Deposits, Alaska, Peninsula, 230.
Wright, F. E., Obsidian from Iceland, 182; Geological Protractor, 233 ; Polariser in Petrographie Micro- scope, 233.
Effects of
ORKSHIRE Geology, Bibliography of, 131. Yunnan-Tibet Border, Land of Deep Corrosions, 209.
EILLER, R., Palwobotanist, 47. Zircon, Monazite, etc., 523. Zoogeography, New Method, 180. Zoological Record, 181, 240. Society, 332, 333.
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